sonic_pi_docs.md

1 Welcome to Sonic Pi

Welcome friend :-)

Welcome to Sonic Pi. Hopefully you're as excited to get started making crazy sounds as I am to show you. It's going to be a really fun ride where you'll learn all about music, synthesis, programming, composition, performance and more.

But wait, how rude of me! Let me introduce myself - I'm Sam Aaron - the chap that created Sonic Pi. You can find me at @samaaron on Twitter and I'd be more than happy to say hello to you. You might also be interested in finding out more about my Live Coding Performances where I code with Sonic Pi live in front of audiences.

If you have any thoughts, or ideas for improving Sonic Pi - please pass them on - feedback is so helpful. You never know, your idea might be the next big feature!

This tutorial is divided up into sections grouped by category. Whilst I've written it to have an easy learning progression from start to finish, feel very free just to dip in and out of sections as you see fit. If you feel that there's something missing, do let me know and I'll consider it for a future version.

Finally, watching others live code is a really great way to learn. I regularly stream live on livecoding.tv/samaaron so please do drop by, say hi and ask me lots of questions :-)

OK, let's get started... 1.1 Live Coding

Live Coding

One of the most exciting aspects of Sonic Pi is that it enables you to write and modify code live to make music, just like you might perform live with a guitar. This means that given some practice you can take Sonic Pi on stage and gig with it.

Free your mind

Before we get into the real details of how Sonic Pi works in the rest of this tutorial, I'd like to give you an experience of what it's like to live code. Don't worry if you don't understand much (or any) of this. Just try to hold onto your seats and enjoy...

A live loop

Let's get started, copy the following code into an empty buffer above:

live_loop :flibble do
  sample :bd_haus, rate: 1
  sleep 0.5
end

Now, press the Run button and you'll hear a nice fast bass drum beating away. If at any time you wish to stop the sound just hit the Stop button. Although don't hit it just yet... Instead, follow these steps:

1. Make sure the bass drum sound is still running
2. Change the sleep value from 0.5 to something higher like 1.
3. Press the Run button again
4. Notice how the drum speed has changed.
5. Finally, remember this moment, this is the first time you've live coded with Sonic Pi and it's unlikely to be your last...

Ok, that was simple enough. Let's add something else into the mix. Above sample :bd_haus add the line sample :ambi_choir, rate: 0.3. Your code should look like this:

live_loop :flibble do
  sample :ambi_choir, rate: 0.3
  sample :bd_haus, rate: 1
  sleep 1
end

Now, play around. Change the rates - what happens when you use high values, or small values or negative values? See what happens when you change the rate: value for the :ambi_choir sample just slightly (say to 0.29). What happens if you choose a really small sleep value? See if you can make it go so fast your computer will stop with an error because it can't keep up (if that happens, just choose a bigger sleep time and hit Run again).

Try commenting one of the sample lines out by adding a # to the beginning:

live_loop :flibble do
  sample :ambi_choir, rate: 0.3
#  sample :bd_haus, rate: 1
  sleep 1
end

Notice how it tells the computer to ignore it, so we don't hear it. This is called a comment. In Sonic Pi we can use comments to remove and add things into the mix.

Finally, let me leave you something fun to play with. Take the code below, and copy it into a spare buffer. Now, don't try to understand it too much other than see that there are two loops - so two things going round at the same time. Now, do what you do best - experiment and play around. Here are some suggestions:

• Try changing the blue rate: values to hear the sample sound change.
• Try changing the sleep times and hear that both loops can spin round at different rates.
• Try uncommenting the sample line (remove the #) and enjoy the sound of the guitar played backwards.
• Try changing any of the blue mix: values to numbers between 0 (not in the mix) and 1 (fully in the mix).

Remember to press Run and you'll hear the change next time the loop goes round. If you end up in a pickle, don't worry - hit Stop, delete the code in the buffer and paste a fresh copy in and you're ready to jam again. Making mistakes is how you'll learn the quickest...

live_loop :guit do
  with_fx :echo, mix: 0.3, phase: 0.25 do
    sample :guit_em9, rate: 0.5
  end
#  sample :guit_em9, rate: -0.5
  sleep 8
end

live_loop :boom do
  with_fx :reverb, room: 1 do
    sample :bd_boom, amp: 10, rate: 1
  end
  sleep 8
end

Now, keep playing and experimenting until your curiosity about how this all actually works kicks in and you start wondering what else you can do with this. You're now ready to read the rest of the tutorial.

So what are you waiting for... 1.2 Exploring the Interface

The Sonic Pi Interface

Sonic Pi has a very simple interface for coding music. Let's spend a little time exploring it.

• A - Play Controls
• B - Editor Controls
• C - Info and Help
• D - Code Editor
• E - Prefs Panel
• F - Log Viewer
• G - Help System

A. Play Controls

These pink buttons are the main controls for starting and stopping sounds. There's the Run button for running the code in the editor, Stop for stopping all running code, Save for saving the code to an external file and Record to create a recording (a WAV file) of the sound playing.

B. Editor Controls

These orange buttons allow you to manipulate the code editor. The Size + and Size - buttons allow you to make the text bigger and smaller. The Align button will neaten the code for you to make it look more professional.

C. Info and Help

These blue buttons give you access to information, help and preferences. The Info button will open up the information window which contains information about Sonic Pi itself - the core team, history, contributors and community. The Help button toggles the help system (F) and the Prefs button toggles the preferences window which allows you to control some basic system parameters.

D. Code Editor

This is the area where you'll write your code and compose/perform music. It's a simple text editor where you can write code, delete it, cut and paste, etc. Think of it like a very basic version of Word or Google Docs. The editor will automatically colour words based on their meaning in the code. This may seem strange at first, but you'll soon find it very useful. For example, you'll know something is a number because it is blue.

E. Prefs Panel

Sonic Pi supports a number of tweakable preferences which can be accessed by toggling the prefs button in the Info and Help button set. This will toggle the visibility of the Prefs Panel which includes a number of options to be changed. Examples are forcing mono mode, inverting stereo, Toggling log output verbosity and also a volume slider and audio selector on the Raspberry Pi.

F. Log Viewer

When you run your code, information about what the program is doing will be displayed in the log viewer. By default, you'll see a message for every sound you create with the exact time the sound was triggered. This is very useful for debugging your code and understanding what your code is doing.

G. Help System

Finally, one of the most important parts of the Sonic Pi interface is the help system which appears at the bottom of the window. This can be toggled on and off by clicking on the blue Help button. The help system contains help and information about all aspects of Sonic Pi including this tutorial, a list of available synths, samples, examples, FX and a full list of all the functions Sonic Pi provides for coding music. 1.3 Learning through Play

Learning through Play

Sonic Pi encourages you to learn about both computing and music through play and experimentation. The most important thing is that you're having fun, and before you know it you'll have accidentally learned how to code, compose and perform.

There are no mistakes

Whilst we're on this subject, let me just give you one piece of advice I've learned over my years of live coding with music - there are no mistakes, only opportunities. This is something I've often heard in relation to jazz but it works equally well with live coding. No matter how experienced you are - from a complete beginner to a seasoned Algoraver, you'll run some code that has a completely unexpected outcome. It might sound insanely cool - in which case run with it. However, it might sound totally jarring and out of place. It doesn't matter that it happened - what matters is what you do next with it. Take the sound, manipulate it and morph it into something awesome. The crowd will go wild.

Start Simple

When you're learning, it's tempting to want to do amazing things now. However, just hold that thought and see it as a distant goal to reach later. For now, instead think of the simplest thing you could write which would be fun and rewarding that's a small step towards the amazing thing you have in your head. Once you have an idea about that simple step, then try and build it, play with it and then see what new ideas it gives you. Before long you'll be too busy having fun and making real progress.

Just make sure to share your work with others! 2 Synths

Synths

OK, enough of the intros - let's get into some sound.

In this section we'll cover the basis of triggering and manipulating synths. Synth is short for synthesiser which is a fancy word for something which creates sounds. Typically synths are quite complicated to use - especially analog synths with many patch wires and modules. However, Sonic Pi gives you much of that power in a very simple and approachable manner.

Don't be fooled by the immediate simplicity of Sonic Pi's interface. You can get very deep into very sophisticated sound manipulation if that's your thing. Hold on to your hats... 2.1 Your First Beeps

Your First Beeps

Take a look at the following code:

play 70

This is where it all starts. Go ahead, copy and paste it into the code window at the top of the app (the big white space under the Run button). Now, press Run...

Beep!

Intense. Press it again. And again. And again...

Woah, crazy, I'm sure you could keep doing that all day. But wait, before you lose yourself in an infinite stream of beeps, try changing the number:

play 75

Can you hear the difference? Try a lower number:

play 60

So, lower numbers make lower pitched beeps and higher numbers make higher pitched beeps. Just like on a piano, the keys at the lower part of the piano (the left hand side) play lower notes and the keys on the higher part of the piano (the right hand side) play higher notes. In fact, the numbers actually relate to notes on the piano. play 47 actually means play the 47th note on the piano. Which means that play 48 is one note up (the next note to the right). It just so happens that the 4th octave C is number 60. Go ahead and play it: play 60.

Don't worry if this means nothing to you - it didn't to me when I first started. All that matters right now is that you know that low numbers make lower beeps and high numbers make higher beeps.

Chords

Playing a note is quite fun, but playing many at the same time can be even better. Try it:

play 72
play 75
play 79

Jazzy! So, when you write multiple plays, they all play at the same time. Try it for yourself - which numbers sound good together? Which sound terrible? Experiment, explore and find out for yourself.

Melody

So, playing notes and chords is fun - but how about a melody? What if you wanted to play one note after another and not at the same time? Well, that's easy, you just need to sleep between the notes:

play 72
sleep 1
play 75
sleep 1
play 79

How lovely, a little arpeggio. So what does the 1 mean in sleep 1? Well it means the duration of the sleep. It actually means sleep for one beat, but for now we can think about it as sleeping for 1 second. So, what if we wanted to make our arpeggio a little faster? Well, we need to use shorter sleep values. What about a half i.e. 0.5:

play 72
sleep 0.5
play 75
sleep 0.5
play 79

Notice how it plays faster. Now, try for yourself, change the times - use different times and notes.

One thing to try is in-between notes such as play 52.3 and play 52.63. There's absolutely no need to stick to standard whole notes. Play around and have fun.

Traditional Note Names

For those of you that already know some musical notation (don't worry if you don't - you don't need it to have fun) you might want to write a melody using note names such as C and F# rather than numbers. Sonic Pi has you covered. You can do the following:

play :C
sleep 0.5
play :D
sleep 0.5
play :E

Remember to put the colon : in front of your note name so that it goes pink. Also, you can specify the octave by adding a number after the note name:

play :C3
sleep 0.5
play :D3
sleep 0.5
play :E4

If you want to make a note sharp, add an s after the note name such as play :Fs3 and if you want to make a note flat, add a b such as play :Eb3.

Now go crazy and have fun making your own tunes. 2.2 Synth Options

Synth Options: Amp and Pan

As well as allowing you to control which note to play or which sample to trigger, Sonic Pi provides a whole range of options to craft and control the sounds. We'll be covering many of these in this tutorial and there's extensive documentation for each in the help system. However, for now we'll introduce two of the most useful: amplitude and pan. First, let's look at what options actually are.

Options

Sonic Pi supports the notion of options (or opts for short) for its synths. Opts are controls you pass to play which modify and control aspects of the sound you hear. Each synth has its own set of opts for finely tuning its sound. However, there are common sets of opts shared by many sounds such as amp: and envelope opts (covered in another section).

Opts have two major parts, their name (the name of the control) and their value (the value you want to set the control at). For example, you might have a opt called cheese: and want to set it with a value of 1.

Opts are passed to calls to play by using a comma , and then the name of the opt such as amp: (don't forget the colon :) and then a space and the value of the opt. For example:

play 50, cheese: 1

(Note that cheese: isn't a valid opt, we're just using it as an example).

You can pass multiple opts by separating them with a comma:

play 50, cheese: 1, beans: 0.5

The order of the opts doesn't matter, so the following is identical:

play 50, beans: 0.5, cheese: 1

Opts that aren't recognised by the synth are just ignored (like cheese and beans which are clearly ridiculous opt names!)

If you accidentally use the same opt twice with different values, the last one wins. For example, beans: here will have the value 2 rather than 0.5:

play 50, beans: 0.5, cheese: 3, eggs: 0.1, beans: 2

Many things in Sonic Pi accept opts, so just spend a little time learning how to use them and you'll be set! Let's play with our first opt: amp:.

Amplitude

Amplitude is a computer representation of the loudness of a sound. A high amplitude produces a loud sound and a low amplitude produces a quiet sound. Just as Sonic Pi uses numbers to represent time and notes, it uses numbers to represent amplitude. An amplitude of 0 is silent (you'll hear nothing) whereas an amplitude of 1 is normal volume. You can even crank up the amplitude higher to 2, 10, 100. However, you should note that when the overall amplitude of all the sounds gets too high, Sonic Pi uses what's called a compressor to squash them all to make sure things aren't too loud for your ears. This can often make the sound muddy and strange. So try to use low amplitudes, i.e. in the range 0 to 0.5 to avoid compression.

Amp it up

To change the amplitude of a sound, you can use the amp: opt. For example, to play at half amplitude pass 0.5:

play 60, amp: 0.5

To play at double amplitude pass 2:

play 60, amp: 2

The amp: opt only modifies the call to play it's associated with. So, in this example, the first call to play is at half volume and the second is back to the default (1):

play 60, amp: 0.5
sleep 0.5
play 65

Of course, you can use different amp: values for each call to play:

play 50, amp: 0.1
sleep 0.25
play 55, amp: 0.2
sleep 0.25
play 57, amp: 0.4
sleep 0.25
play 62, amp: 1

Panning

Another fun opt to use is pan: which controls the panning of a sound in stereo. Panning a sound to the left means that you hear it out of the left speaker, and panning it to the right means you hear it out of your right speaker. For our values, we use a -1 to represent fully left, 0 to represent center and 1 to represent fully right in the stereo field. Of course, we're free to use any value between -1 and 1 to control the exact positioning of our sound.

Let's play a beep out of the left speaker:

play 60, pan: -1

Now, let's play it out of the right speaker:

play 60, pan: 1

Finally let's play it back out of the center of both (the default position):

play 60, pan: 0

Now, go and have fun changing the amplitude and panning of your sounds! 2.3 Switching Synths

Switching Synths

So far we've had quite a lot of fun making beeps. However, you're probably starting to get bored of the basic beep noise. Is that all Sonic Pi has to offer? Surely there's more to live coding than just playing beeps? Yes there is, and in this section we'll explore the exciting range of sounds that Sonic Pi has to offer.

Synths

Sonic Pi has a range of instruments it calls synths which is short for synthesisers. Whereas samples represent pre-recorded sounds, synths are capable of generating new sounds depending on how you control them (which we'll explore later in this tutorial). Sonic Pi's synths are very powerful and expressive and you'll have a lot of fun exploring and playing with them. First, let's learn how to select the current synth to use.

Buzzy saws and prophets

A fun sound is the saw wave - let's give it a try:

use_synth :saw
play 38
sleep 0.25
play 50
sleep 0.25
play 62
sleep 0.25

Let's try another sound - the prophet:

use_synth :prophet
play 38
sleep 0.25
play 50
sleep 0.25
play 62
sleep 0.25

How about combining two sounds. First one after another:

use_synth :saw
play 38
sleep 0.25
play 50
sleep 0.25
use_synth :prophet
play 57
sleep 0.25

Now at the same time:

use_synth :tb303
play 38
sleep 0.25
use_synth :dsaw
play 50
sleep 0.25
use_synth :prophet
play 57
sleep 0.25

Notice that the use_synth command only affects the following calls to play. Think of it like a big switch - new calls to play will play whatever synth it's currently pointing to. You can move the switch to a new synth with use_synth.

Discovering Synths

To see which synths Sonic Pi has for you to play with take a look at the Synths option in the far left vertical menu (above Fx). There are over 20 to choose from. Here are a few of my favourites:

• :prophet
• :dsaw
• :fm
• :tb303
• :pulse

Now play around with switching synths during your music. Have fun combining synths to make new sounds as well as using different synths for different sections of your music. 2.4 Duration with Envelopes

Duration with Envelopes

In an earlier section, we looked at how we can use the sleep command to control when to trigger our sounds. However, we haven't yet been able to control the duration of our sounds.

In order to give us a simple, yet powerful means of controlling the duration of our sounds, Sonic Pi provides the notion of an ADSR amplitude envelope (we'll cover what ADSR means later in this section). An amplitude envelope offers two useful aspects of control:

• control over the duration of a sound
• control over the amplitude of a sound

Duration

The duration is the length the sound lasts for. A longer duration means that you hear the sound for longer. Sonic Pi's sounds all have a controllable amplitude envelope, and the total duration of that envelope is the duration of the sound. Therefore, by controlling the envelope you control the duration.

Amplitude

The ADSR envelope not only controls duration, it also gives you fine control over the amplitude of the sound. All audible sounds start and end silent and contain some non-silent part in-between. Envelopes allow you to slide and hold the amplitude of non-silent parts of the sound. It's like giving someone instructions on how to turn up and down the volume of a guitar amplifier. For example you might ask someone to "start at silence, slowly move up to full volume, hold it for a bit, then quickly fall back to silence." Sonic Pi allows you to program exactly this behaviour with envelopes.

Just to recap, as we have seen before, an amplitude of 0 is silence and an amplitude of 1 is normal volume.

Now, let us look at each of the parts of the envelopes in turn.

Release Phase

The only part of the envelope that's used by default is the release time. This is the time it takes for the synth's sound to fade out. All synths have a release time of 1 which means that by default they have a duration of 1 beat (which at the default BPM of 60 is 1 second):

play 70

The note will be audible for 1 second. Go ahead and time it :-) This is short hand for the longer more explicit version:

play 70, release: 1

Notice how this sounds exactly the same (the sound lasts for one second). However, it's now very easy to change the duration by modifying the value of the release: opt:

play 60, release: 2

We can make the synth sound for a very short amount of time by using a very small release time:

play 60, release: 0.2

The duration of the release of the sound is called the release phase and by default is a linear transition (i.e. a straight line). The following diagram illustrates this transition:

The vertical line at the far left of the diagram shows that the sound starts at 0 amplitude, but goes up to full amplitude immediately (this is the attack phase which we'll cover next). Once at full amplitude it then moves in a straight line down to zero taking the amount of time specified by release:. Longer release times produce longer synth fade outs.

You can therefore change the duration of your sound by changing the release time. Have a play adding release times to your music.

Attack Phase

By default, the attack phase is 0 for all synths which means they move from 0 amplitude to 1 immediately. This gives the synth an initial percussive sound. However, you may wish to fade your sound in. This can be achieved with the attack: opt. Try fading in some sounds:

play 60, attack: 2
sleep 3
play 65, attack: 0.5

You may use multiple opts at the same time. For example for a short attack and a long release try:

play 60, attack: 0.7, release: 4

This short attack and long release envelope is illustrated in the following diagram:

Of course, you may switch things around. Try a long attack and a short release:

play 60, attack: 4, release: 0.7

Finally, you can also have both short attack and release times for shorter sounds.

play 60, attack: 0.5, release: 0.5

Sustain Phase

In addition to specifying attack and release times, you may also specify a sustain time to control the sustain phase. This is the time for which the sound is maintained at full amplitude between the attack and release phases.

play 60, attack: 0.3, sustain: 1, release: 1

The sustain time is useful for important sounds you wish to give full presence in the mix before entering an optional release phase. Of course, it's totally valid to set both the attack: and release: opts to 0 and just use the sustain to have absolutely no fade in or fade out to the sound. However, be warned, a release of 0 can produce clicks in the audio and it's often better to use a very small value such as 0.2.

Decay Phase

For an extra level of control, you can also specify a decay time. This is a phase of the envelope that fits between the attack and sustain phases and specifies a time where the amplitude will drop from the attack_level: to the decay_level: (which unless you explicitly set it will be set to the sustain_level:). By default, the decay: opt is 0 and both the attack and sustain levels are 1 so you'll need to specify them for the decay time to have any effect:

play 60, attack: 0.1, attack_level: 1, decay: 0.2, sustain_level: 0.4, sustain: 1, release: 0.5

Decay Level

One last trick is that although the decay_level: opt defaults to be the same value as sustain_level: you can explicitly set them to different values for full control over the envelope. This allows you to to create envelopes such as the following:

play 60, attack: 0.1, attack_level: 1, decay: 0.2, decay_level: 0.3, sustain: 1, sustain_level: 0.4, release: 0.5

It's also possible to set the decay_level: to be higher than sustain_level::

play 60, attack: 0.1, attack_level: 0.1, decay: 0.2, decay_level: 1, sustain: 0.5, sustain_level: 0.8, release: 1.5

ADSR Envelopes

So to summarise, Sonic Pi's ADSR envelopes have the following phases:

1. attack - time from 0 amplitude to the attack_level,
2. decay - time to move amplitude from attack_level to decay_level,
3. sustain - time to move the amplitude from decay_level to sustain_level,
4. release - time to move amplitude from sustain_level to 0

It's important to note that the duration of a sound is the summation of the times of each of these phases. Therefore the following sound will have a duration of 0.5 + 1 + 2 + 0.5 = 4 beats:

play 60, attack: 0.5, attack_level: 1, decay: 1, sustain_level: 0.4, sustain: 2, release: 0.5

Now go and have a play adding envelopes to your sounds... 3 Samples

Samples

Another great way to develop your music is to use pre-recorded sounds. In great hip-hop tradition, we call these pre-recorded sounds samples. So, if you take a microphone outside, go and record the gentle sound of rain hitting canvas, you've just created a sample.

Sonic Pi lets you do lots of fun things with samples. Not only does it ship with over 90 public domain samples ready for you to jam with, it lets you play and manipulate your own. Let's get to it... 3.1 Triggering Samples

Triggering Samples

Playing beeps is only the beginning. Something that's a lot of fun is triggering pre-recorded samples. Try it:

sample :ambi_lunar_land

Sonic Pi includes many samples for you to play with. You can use them just like you use the play command. To play multiple samples and notes just write them one after another:

play 36
play 48
sample :ambi_lunar_land
sample :ambi_drone

If you want to space them out in time, use the sleep command:

sample :ambi_lunar_land
sleep 1
play 48
sleep 0.5
play 36
sample :ambi_drone
sleep 1
play 36

Notice how Sonic Pi doesn't wait for a sound to finish before starting the next sound. The sleep command only describes the separation of the triggering of the sounds. This allows you to easily layer sounds together creating interesting overlap effects. Later in this tutorial we'll take a look at controlling the duration of sounds with envelopes.

Discovering Samples

There are two ways to discover the range of samples provided in Sonic Pi. First, you can use this help system. Click on Samples in the far left vertical menu, choose your category and then you'll see a list of available sounds.

Alternatively you can use the auto-completion system. Simply type the start of a sample group such as: sample :ambi_ and you'll see a drop-down of sample names appear for you to select. Try the following category prefixes:

• :ambi_
• :bass_
• :elec_
• :perc_
• :guit_
• :drum_
• :misc_
• :bd_

Now start mixing samples into your compositions! 3.2 Sample Parameters

Sample Parameters: Amp and Pan

As we saw with synths, we can easily control our sounds with parameters. Samples support exactly the same parameterisation mechanism. Let's revisit our friends amp: and pan:.

Amping samples

You can change the amplitude of samples with exactly the same approach you used for synths:

sample :ambi_lunar_land, amp: 0.5

Panning samples

We're also able to use the pan: parameter on samples. For example, here's how we'd play the amen break in the left ear and then half way through play it again through the right ear:

sample :loop_amen, pan: -1
sleep 0.877
sample :loop_amen, pan: 1

Note that 0.877 is half the duration of the :loop_amen sample in seconds.

Finally, note that if you set some synth defaults with use_synth_defaults (which we will discuss later), these will be ignored by sample. 3.3 Stretching Samples

Stretching Samples

Now that we can play a variety of synths and samples to create some music, it's time to learn how to modify both the synths and samples to make the music even more unique and interesting. First, let's explore the ability to stretch and squash samples.

Sample Representation

Samples are pre-recorded sounds stored as numbers which represent how to move the speaker cone to reproduce the sound. The speaker cone can move in and out, and so the numbers just need to represent how far in and out the cone needs to be for each moment in time. To be able to faithfully reproduce a recorded sound the sample typically needs to store many thousands of numbers per second! Sonic Pi takes this list of numbers and feeds them at the right speed to move your computer's speaker in and out in just the right way to reproduce the sound. However, it's also fun to change the speed with which the numbers are fed to the speaker to change the sound.

Changing Rate

Let's play with one of the ambient sounds: :ambi_choir. To play it with the default rate, you can pass a rate: opt to sample:

sample :ambi_choir, rate: 1

This plays it at normal rate (1), so nothing special yet. However, we're free to change that number to something else. How about 0.5:

sample :ambi_choir, rate: 0.5

Woah! What's going on here? Well, two things. Firstly, the sample takes twice as long to play, secondly the sound is an octave lower. Let's explore these things in a little more detail.

Let's stretch

A sample that's fun to stretch and compress is the Amen Break. At normal rate, we might imagine throwing it into a drum 'n' bass track:

sample :loop_amen

However by changing the rate we can switch up genres. Try half speed for old school hip-hop:

sample :loop_amen, rate: 0.5

If we speed it up, we enter jungle territory:

sample :loop_amen, rate: 1.5

Now for our final party trick - let's see what happens if we use a negative rate:

sample :loop_amen, rate: -1

Woah! It plays it backwards! Now try playing with lots of different samples at different rates. Try very fast rates. Try crazy slow rates. See what interesting sounds you can produce.

A Simple Explanation of Sample Rate

A useful way to think of samples is as springs. Playback rate is like squashing and stretching the spring. If you play the sample at rate 2, you're squashing the spring to half its normal length. The sample therefore takes half the amount of time to play as it's shorter. If you play the sample at half rate, you're stretching the spring to double its length. The sample therefore takes twice the amount of time to play as it's longer. The more you squash (higher rate), the shorter it gets, the more you stretch (lower rate), the longer it gets.

Compressing a spring increases its density (the number of coils per cm)

• this is similar to the sample sounding higher pitched. Stretching the spring decreases its density and is similar to the sound having a lower pitch.

The Maths Behind Sample Rate

(This section is provided for those that are interested in the details. Please feel free to skip it...)

As we saw above, a sample is represented by a big long list of numbers representing where the speaker should be through time. We can take this list of numbers and use it to draw a graph which would look similar to this:

You might have seen pictures like this before. It's called the waveform of a sample. It's just a graph of numbers. Typically a waveform like this will have 44100 points of data per second (this is due to the Nyquist-Shannon sampling theorem). So, if the sample lasts for 2 seconds, the waveform will be represented by 88200 numbers which we would feed to the speaker at a rate of 44100 points per second. Of course, we could feed it at double rate which would be 88200 points per second. This would therefore take only 1 second to play back. We could also play it back at half rate which would be 22050 points per second taking 4 seconds to play back.

The duration of the sample is affected by the playback rate:

• Doubling the playback rate halves the playback time,
• Halving the playback rate doubles the playback time,
• Using a playback rate of one fourth quadruples the playback time,
• Using a playback rate of 1/10 makes playback last 10 times longer.

We can represent this with the formula:

new_sample_duration = (1 / rate) * sample_duration 

Changing the playback rate also affects the pitch of the sample. The frequency or pitch of a waveform is determined by how fast it moves up and down. Our brains somehow turn fast movement of speakers into high notes and slow movement of speakers into low notes. This is why you can sometimes even see a big bass speaker move as it pumps out super low bass - it's actually moving a lot slower in and out than a speaker producing higher notes.

If you take a waveform and squash it it will move up and down more times per second. This will make it sound higher pitched. It turns out that doubling the amount of up and down movements (oscillations) doubles the frequency. So, playing your sample at double rate will double the frequency you hear it. Also, halving the rate will halve the frequency. Other rates will affect the frequency accordingly. 3.4 Enveloped Samples

Enveloped Samples

It is also possible to modify the duration and amplitude of a sample using an ADSR envelope. However, this works slightly differently to the ADSR envelope available on synths. Sample envelopes only allow you to reduce the amplitude and duration of a sample - and never to increase it. The sample will stop when either the sample has finished playing or the envelope has completed - whichever is first. So, if you use a very long release:, it won't extend the duration of the sample.

Amen Envelopes

Let's return to our trusty friend the Amen Break:

sample :loop_amen

With no opts, we hear the full sample at full amplitude. If we want to fade this in over 1 second we can use the attack: param:

sample :loop_amen, attack: 1

For a shorter fade in, choose a shorter attack value:

sample :loop_amen, attack: 0.3

Auto Sustain

Where the ADSR envelope's behaviour differs from the standard synth envelope is in the sustain value. In the standard synth envelope, the sustain defaulted to 0 unless you set it manually. With samples, the sustain value defaults to an automagical value - the time left to play the rest of the sample. This is why we hear the full sample when we pass no defaults. If the attack, decay, sustain and release values were all 0 we'd never hear a peep. Sonic Pi therefore calculates how long the sample is, deducts any attack, decay and release times and uses the result as your sustain time. If the attack, decay and release values add up to more than the duration of the sample, the sustain is simply set to 0.

Fade Outs

To explore this, let's consider our Amen break in more detail. If we ask Sonic Pi how long the sample is:

print sample_duration :loop_amen

It will print out 1.753310657596372 which is the length of the sample in seconds. Let's just round that to 1.75 for convenience here. Now, if we set the release to 0.75, something surprising will happen:

sample :loop_amen, release: 0.75

It will play the first second of the sample at full amplitude before then fading out over a period of 0.75 seconds. This is the auto sustain in action. By default, the release always works from the end of the sample. If our sample was 10.75 seconds long, it would play the first 10 seconds at full amplitude before fading out over 0.75s.

Remember: by default, release: fades out at the end of a sample.

Fade In and Out

We can use both attack: and release: together with the auto sustain behaviour to fade both in and out over the duration of the sample:

sample :loop_amen, attack: 0.75, release: 0.75

As the full duration of the sample is 1.75s and our attack and release phases add up to 1.5s, the sustain is automatically set to 0.25s. This allows us to easily fade the sample in and out.

Explicit sustain

We can easily get back to our normal synth ADSR behaviour by manually setting sustain: to a value such as 0:

sample :loop_amen, sustain: 0, release: 0.75

Now, our sample only plays for 0.75 seconds in total. With the default for attack: and decay: at 0, the sample jumps straight to full amplitude, sustains there for 0s then releases back down to 0 amplitude over the release period - 0.75s.

Percussive cymbals

We can use this behaviour to good effect to turn longer sounding samples into shorter, more percussive versions. Consider the sample :drum_cymbal_open:

sample :drum_cymbal_open

You can hear the cymbal sound ringing out over a period of time. However, we can use our envelope to make it more percussive:

sample :drum_cymbal_open, attack: 0.01, sustain: 0, release: 0.1

You can then emulate hitting the cymbal and then dampening it by increasing the sustain period:

sample :drum_cymbal_open, attack: 0.01, sustain: 0.3, release: 0.1

Now go and have fun putting envelopes over the samples. Try changing the rate too for really interesting results. 3.5 Partial Samples

Partial Samples

This section will conclude our exploration of Sonic Pi's sample player. Let's do a quick recap. So far we've looked at how we can trigger samples:

sample :loop_amen

We then looked at how we can change the rate of samples such as playing them at half speed:

sample :loop_amen, rate: 0.5

Next, we looked at how we could fade a sample in (let's do it at half speed):

sample :loop_amen, rate: 0.5, attack: 1

We also looked at how we could use the start of a sample percussively by giving sustain: an explicit value and setting both the attack and release to be short values:

sample :loop_amen, rate: 2, attack: 0.01, sustain: 0, release: 0.35

However, wouldn't it be nice if we didn't have to always start at the beginning of the sample? Wouldn't it also be nice if we didn't have to always finish at the end of the sample?

Choosing a starting point

It is possible to choose an arbitrary starting point in the sample as a value between 0 and 1 where 0 is the start of the sample, 1 is the end and 0.5 is half way through the sample. Let's try playing only the last half of the amen break:

sample :loop_amen, start: 0.5

How about the last quarter of the sample:

sample :loop_amen, start: 0.75

Choosing a finish point

Similarly, it is possible to choose an arbitrary finish point in the sample as a value between 0 and 1. Let's finish the amen break half way through:

sample :loop_amen, finish: 0.5

Specifying start and finish

Of course, we can combine these two to play arbitrary segments of the audio file. How about only a small section in the middle:

sample :loop_amen, start: 0.4, finish: 0.6

What happens if we choose a start position after the finish position?

sample :loop_amen, start: 0.6, finish: 0.4

Cool! It plays it backwards!

Combining with rate

We can combine this new ability to play arbitrary segments of audio with our friend rate:. For example, we can play a very small section of the middle of the amen break very slowly:

sample :loop_amen, start: 0.5, finish: 0.7, rate: 0.2

Combining with envelopes

Finally, we can combine all of this with our ADSR envelopes to produce interesting results:

sample :loop_amen, start: 0.5, finish: 0.8, rate: -0.2, attack: 0.3, release: 1

Now go and have a play mashing up samples with all of this fun stuff... 3.6 External Samples

External Samples

Whilst the built-in samples can get you up and started quickly, you might wish to experiment with other recorded sounds in your music. Sonic Pi totally supports this. First though, let's have a quick discussion on the portability of your piece.

Portability

When you compose your piece purely with built-in synths and samples, the code is all you need to faithfully reproduce your music. Think about that for a moment - that's amazing! A simple piece of text you can email around or stick in a Gist represents everything you need to reproduce your sounds. That makes it really easy to share with your friends as they just need to get hold of the code.

However, if you start using your own pre-recorded samples, you lose this portability. This is because to reproduce your music other people not only need your code, they need your samples too. This limits the ability for others to manipulate, mash-up and experiment with your work. Of course this shouldn't stop you from using your own samples, it's just something to consider.

ruby

Local Samples

So how do you play any arbitrary WAV or AIFF file on your computer? All you need to do is pass the path of that file to sample:

# Raspberry Pi, Mac, Linux
sample "/Users/sam/Desktop/my-sound.wav"
# Windows
sample "C:/Users/sam/Desktop/my-sound.wav"

Sonic Pi will automatically load and play the sample. You can also pass all the standard params you're used to passing sample:

# Raspberry Pi, Mac, Linux
sample "/Users/sam/Desktop/my-sound.wav", rate: 0.5, amp: 0.3
# Windows
sample "C:/Users/sam/Desktop/my-sound.wav", rate: 0.5, amp: 0.3

4 Randomisation

Randomisation

A great way to add some interest into your music is using some random numbers. Sonic Pi has some great functionality for adding randomness to your music, but before we start we need to learn a shocking truth: in Sonic Pi random is not truly random. What on earth does this mean? Well, let's see.

Repeatability

A really useful random function is rrand which will give you a random value between two numbers - a min and a max. (rrand is short for ranged random). Let's try playing a random note:

play rrand(50, 95)

Ooh, it played a random note. It played note 83.7527. A nice random note between 50 and 95. Woah, wait, did I just predict the exact random note you got too? Something fishy is going on here. Try running the code again. What? It chose 83.7527 again? That can't be random!

The answer is that it is not truly random, it's pseudo-random. Sonic Pi will give you random-like numbers in a repeatable manner. This is very useful for ensuring that the music you create on your machine sounds identical on everybody else's machine - even if you use some randomness in your composition.

Of course, in a given piece of music, if it 'randomly' chose 83.7527 every time, then it wouldn't be very interesting. However, it doesn't. Try the following:

loop do
  play rrand(50, 95)
  sleep 0.5
end 

Yes! It finally sounds random. Within a given run subsequent calls to random functions will return random values. However, the next run will produce exactly the same sequence of random values and sound exactly the same. It's as if all Sonic Pi code went back in time to exactly the same point every time the Run button was pressed. It's the Groundhog Day of music synthesis!

Haunted Bells

A lovely illustration of randomisation in action is the haunted bells example which loops the :perc_bell sample with a random rate and sleep time between bell sounds:

loop do
  sample :perc_bell, rate: (rrand 0.125, 1.5)
  sleep rrand(0.2, 2)
end

Random cutoff

Another fun example of randomisation is to modify the cutoff of a synth randomly. A great synth to try this out on is the :tb303 emulator:

use_synth :tb303

loop do
  play 50, release: 0.1, cutoff: rrand(60, 120)
  sleep 0.125
end

Random seeds

So, what if you don't like this particular sequence of random numbers Sonic Pi provides? Well it's totally possible to choose a different starting point via use_random_seed. The default seed happens to be 0, so choose a different seed for a different random experience!

Consider the following:

5.times do
  play rrand(50, 100)
  sleep 0.5
end

Every time you run this code, you'll hear the same sequence of 5 notes. To get a different sequence simply change the seed:

use_random_seed 40
5.times do
  play rrand(50, 100)
  sleep 0.5
end

This will produce a different sequence of 5 notes. By changing the seed and listening to the results you can find something that you like - and when you share it with others, they will hear exactly what you heard too.

Let's have a look at some other useful random functions.

choose

A very common thing to do is to choose an item randomly from a list of known items. For example, I may want to play one note from the following: 60, 65 or 72. I can achieve this with choose which lets me choose an item from a list. First, I need to put my numbers in a list which is done by wrapping them in square brackets and separating them with commas: [60, 65, 72]. Next I just need to pass them to choose:

choose([60, 65, 72])

Let's hear what that sounds like:

loop do
  play choose([60, 65, 72])
  sleep 1
end

rrand

We've already seen rrand, but let's run over it again. It returns a random number between two values exclusively. That means it will never return either the top or bottom number - always something in between the two. The number will always be a float - meaning it's not a whole number but a fraction of a number. Examples of floats returned by rrand(20, 110):

• 87.5054931640625
• 86.05255126953125
• 61.77825927734375

rrand_i

Occasionally you'll want a whole random number, not a float. This is where rrand_i comes to the rescue. It works similarly to rrand except it may return the min and max values as potential random values (which means it's inclusive rather than exclusive of the range). Examples of numbers returned by rrand_i(20, 110) are:

• 88
• 86
• 62

rand

This will return a random float between 0 (inclusive) and the max value you specify (exclusive). By default it will return a value between 0 and one. It's therefore useful for choosing random amp: values:

loop do
  play 60, amp: rand
  sleep 0.25
end

rand_i

Similar to the relationship between rrand_i and rrand, rand_i will return a random whole number between 0 and the max value you specify.

dice

Sometimes you want to emulate a dice throw - this is a special case of rrand_i where the lower value is always 1. A call to dice requires you to specify the number of sides on the dice. A standard dice has 6 sides, so dice(6) will act very similarly - returning values of either 1, 2, 3, 4, 5, or 6. However, just like fantasy role-play games, you might find value in a 4 sided dice, or a 12 sided dice, or a 20 sided dice - perhaps even a 120 sided dice!

one_in

Finally you may wish to emulate throwing the top score of a dice such as a 6 in a standard dice. one_in therefore returns true with a probability of one in the number of sides on the dice. Therefore one_in(6) will return true with a probability of 1 in 6 or false otherwise. True and false values are very useful for if statements which we will cover in a subsequent section of this tutorial.

Now, go and jumble up your code with some randomness! 5 Programming Structures

Programming Structures

Now that you've learned the basics of creating sounds with play and sample and creating simple melodies and rhythms by sleeping between sounds, you might be wondering what else the world of code can offer you...

Well, you're in for an exciting treat! It turns out that basic programming structures such as looping, conditionals, functions and threads give you amazingly powerful tools to express your musical ideas.

Let's get stuck in with the basics... 5.1 Blocks

Blocks

A structure you'll see a lot in Sonic Pi is the block. Blocks allow us to do useful things with large chunks of code. For example, with synth and sample parameters we were able to change something that happened on a single line. However, sometimes we want to do something meaningful to a number of lines of code. For example, we may wish to loop it, to add reverb to it, to only run it 1 time out of 5, etc. Consider the following code:

play 50
sleep 0.5
sample :elec_plip
sleep 0.5
play 62

To do something with a chunk of code, we need to tell Sonic Pi where the code block starts and where it ends. We use do for start and end for end. For example:

do
  play 50
  sleep 0.5
  sample :elec_plip
  sleep 0.5
  play 62
end

However, this isn't yet complete and won't work (try it and you'll get an error) as we haven't told Sonic Pi what we want to do with this do/end block. We tell Sonic Pi this by writing some special code before the do. We'll see a number of these special pieces of code later on in this tutorial. For now, it's important to know that wrapping your code within do and end tells Sonic Pi you wish to do something special with that chunk of code. 5.2 Iteration and Loops

Iteration and Loops

So far we've spent a lot of time looking at the different sounds you can make with play and sample blocks. We've also learned how to trigger these sounds through time using sleep.

As you've probably found out, there's a lot of fun you can have with these basic building blocks. However, a whole new dimension of fun opens up when you start using the power of code to structure your music and compositions. In the next few sections we'll explore some of these powerful new tools. First up is iteration and loops.

Repetition

Have you written some code you'd like to repeat a few times? For example, you might have something like this:

play 50
sleep 0.5
sample :elec_blup
sleep 0.5
play 62
sleep 0.25

What if we wished to repeat this 3 times? Well, we could do something simple and just copy and paste it three times:

play 50
sleep 0.5
sample :elec_blup
sleep 0.5
play 62
sleep 0.25

play 50
sleep 0.5
sample :elec_blup
sleep 0.5
play 62
sleep 0.25

play 50
sleep 0.5
sample :elec_blup
sleep 0.5
play 62
sleep 0.25

Now that's a lot of code! What happens if you want to change the sample to :elec_plip? You're going to have to find all the places with the original :elec_blup and switch them over. More importantly, what if you wanted to repeat the original piece of code 50 times or 1000? Now that would be a lot of code, and a lot of lines of code to alter if you wanted to make a change.

Iteration

In fact, repeating the code should be as easy as saying do this three times. Well, it pretty much is. Remember our old friend the code block? We can use it to mark the start and end of the code we'd like to repeat three times. We then use the special code 3.times. So, instead of writing do this three times, we write 3.times do - that's not too hard. Just remember to write end at the end of the code you'd like to repeat:

3.times do
  play 50
  sleep 0.5
  sample :elec_blup
  sleep 0.5
  play 62
  sleep 0.25
end

Now isn't that much neater than cutting and pasting! We can use this to create lots of nice repeating structures:

4.times do
  play 50
  sleep 0.5
end

8.times do
  play 55, release: 0.2
  sleep 0.25
end

4.times do
  play 50
  sleep 0.5
end

Nesting Iterations

We can put iterations inside other iterations to create interesting patterns. For example:

4.times do
  sample :drum_heavy_kick
  2.times do
    sample :elec_blip2, rate: 2
    sleep 0.25
  end
  sample :elec_snare
  4.times do
    sample :drum_tom_mid_soft
    sleep 0.125
  end
end

Looping

If you want something to repeat a lot of times, you might find yourself using really large numbers such as 1000.times do. In this case, you're probably better off asking Sonic Pi to repeat forever (at least until you press the stop button!). Let's loop the amen break forever:

loop do
  sample :loop_amen
  sleep sample_duration :loop_amen
end

The important thing to know about loops is that they act like black holes for code. Once the code enters a loop it can never leave until you press stop - it will just go round and round the loop forever. This means if you have code after the loop you will never hear it. For example, the cymbal after this loop will never play:

loop do
  play 50
  sleep 1
end

sample :drum_cymbal_open

Now, get structuring your code with iteration and loops! 5.3 Conditionals

Conditionals

A common thing you'll likely find yourself wanting to do is to not only play a random note (see the previous section on randomness) but also make a random decision and based on the outcome run some code or some other code. For example, you might want to randomly play a drum or a cymbal. We can achieve this with an if statement.

Flipping a Coin

So, let's flip a coin: if it's heads, play a drum, if it's tails, play a cymbal. Easy. We can emulate a coin flip with our one_in function (introduced in the section on randomness) specifying a probability of 1 in 2: one_in(2). We can then use the result of this to decide between two pieces of code, the code to play the drum and the code to play the cymbal:

loop do

  if one_in(2)
    sample :drum_heavy_kick
  else
    sample :drum_cymbal_closed
  end
  
  sleep 0.5
  
end

Notice that if statements have three parts:

• The question to ask
• The first choice of code to run (if the answer to the question is yes)
• The second choice of code to run (if the answer to the question is no)

Typically in programming languages, the notion of yes is represented by the term true and the notion of no is represented by the term false. So we need to find a question that will give us a true or false answer which is exactly what one_in does.

Notice how the first choice is wrapped between the if and the else and the second choice is wrapped between the else and the end. Just like do/end blocks you can put multiple lines of code in either place. For example:

loop do

  if one_in(2)
    sample :drum_heavy_kick
    sleep 0.5
  else
    sample :drum_cymbal_closed
    sleep 0.25
  end
  
end

This time we're sleeping for a different amount of time depending on which choice we make.

Simple if

Sometimes you want to optionally execute just one line of code. This is possible by placing if and then the question at the end. For example:

use_synth :dsaw

loop do
  play 50, amp: 0.3, release: 2
  play 53, amp: 0.3, release: 2 if one_in(2)
  play 57, amp: 0.3, release: 2 if one_in(3)
  play 60, amp: 0.3, release: 2 if one_in(4)
  sleep 1.5
end

This will play chords of different numbers with the chance of each note playing having a different probability. 5.4 Threads

Threads

So you've made your killer bassline and a phat beat. How do you play them at the same time? One solution is to weave them together manually - play some bass, then a bit of drums, then more bass... However, the timing soon gets hard to think about, especially when you start weaving in more elements.

What if Sonic Pi could weave things for you automatically? Well, it can, and you do it with a special thing called a thread.

Infinite Loops

To keep this example simple, you'll have to imagine that this is a phat beat and a killer bassline:

loop do
  sample :drum_heavy_kick
  sleep 1
end

loop do
  use_synth :fm
  play 40, release: 0.2
  sleep 0.5
end

As we've discussed previously, loops are like black holes for the program. Once you enter a loop you can never exit from it until you hit stop. How do we play both loops at the same time? We have to tell Sonic Pi that we want to start something at the same time as the rest of the code. This is where threads come to the rescue.

Threads to the Rescue

in_thread do
  loop do
    sample :drum_heavy_kick
    sleep 1
  end
end

loop do
  use_synth :fm
  play 40, release: 0.2
  sleep 0.5
end

By wrapping the first loop in an in_thread do/end block we tell Sonic Pi to run the contents of the do/end block at exactly the same time as the next statement after the do/end block (which happens to be the second loop). Try it and you'll hear both the drums and the bassline weaved together!

Now, what if we wanted to add a synth on top. Something like:

in_thread do
  loop do
    sample :drum_heavy_kick
    sleep 1
  end
end

loop do
  use_synth :fm
  play 40, release: 0.2
  sleep 0.5
end

loop do
  use_synth :zawa
  play 52, release: 2.5, phase: 2, amp: 0.5
  sleep 2
end

Now we have the same problem as before. The first loop is played at the same time as the second loop due to the in_thread. However, the third loop is never reached. We therefore need another thread:

in_thread do
  loop do
    sample :drum_heavy_kick
    sleep 1
  end
end

in_thread do
  loop do
    use_synth :fm
    play 40, release: 0.2
    sleep 0.5
  end
end

loop do
  use_synth :zawa
  play 52, release: 2.5, phase: 2, amp: 0.5
  sleep 2
end

Runs as threads

What may surprise you is that when you press the Run button, you're actually creating a new thread for the code to run. This is why pressing it multiple times will layer sounds over each other. As the runs themselves are threads, they will automatically weave the sounds together for you.

Scope

As you learn how to master Sonic Pi, you'll learn that threads are the most important building blocks for your music. One of the important jobs they have is to isolate the notion of current settings from other threads. What does this mean? Well, when you switch synths using use_synth you're actually just switching the synth in the current thread - no other thread will have their synth switched. Let's see this in action:

play 50
sleep 1

in_thread do
  use_synth :tb303
  play 50
end

sleep 1
play 50

Notice how the middle sound was different to the others? The use_synth statement only affected the thread it was in and not the outer main run thread.

Inheritance

When you create a new thread with in_thread, the new thread will automatically inherit all of the current settings from the current thread. Let's see that:

use_synth :tb303
play 50
sleep 1

in_thread do
  play 55
end

Notice how the second note is played with the :tb303 synth even though it was played from a separate thread? Any of the settings modified with the various use_* functions will behave in the same way.

When threads are created, they inherit all the settings from their parent but they don't share any changes back.

Naming Threads

Finally, we can give our threads names:

in_thread(name: :bass) do
  loop do
    use_synth :prophet
    play chord(:e2, :m7).choose, release: 0.6
    sleep 0.5
  end
end

in_thread(name: :drums) do
  loop do
    sample :elec_snare
    sleep 1
  end
end

Look at the log pane when you run this code. See how the log reports the name of the thread with the message?

[Run 36, Time 4.0, Thread :bass]
 |- synth :prophet, {release: 0.6, note: 47}

Only One Thread per Name Allowed

One last thing to know about named threads is that only one thread of a given name may be running at the same time. Let's explore this. Consider the following code:

in_thread do
  loop do
    sample :loop_amen
    sleep sample_duration :loop_amen
  end
end

Go ahead and paste that into a buffer and press the Run button. Press it again a couple of times. Listen to the cacophony of multiple amen breaks looping out of time with each other. Ok, you can press Stop now.

This is the behaviour we've seen again and again - if you press the Run button, sound layers on top of any existing sound. Therefore if you have a loop and press the Run button three times, you'll have three layers of loops playing simultaneously.

However, with named threads it is different:

in_thread(name: :amen) do
  loop do
    sample :loop_amen
    sleep sample_duration :loop_amen
  end
end

Try pressing the Run button multiple times with this code. You'll only ever hear one amen break loop. You'll also see this in the log:

==> Skipping thread creation: thread with name :amen already exists.

Sonic Pi is telling you that a thread with the name :amen is already playing, so it's not creating another.

This behaviour may not seem immediately useful to you now - but it will be very handy when we start to live code... 5.5 Functions

Functions

Once you start writing lots of code, you may wish to find a way to organise and structure things to make them tidier and easier to understand. Functions are a very powerful way to do this. They give us the ability to give a name to a bunch of code. Let's take a look.

Defining functions

define :foo do
  play 50
  sleep 1
  play 55
  sleep 2
end

Here, we've defined a new function called foo. We do this with our old friend the do/end block and the magic word define followed by the name we wish to give to our function. We didn't have to call it foo, we could have called it anything we want such as bar, baz or ideally something meaningful to you like main_section or lead_riff.

Remember to prepend a colon : to the name of your function when you define it.

Calling functions

Once we have defined our function we can call it by just writing its name:

define :foo do
  play 50
  sleep 1
  play 55
  sleep 0.5
end

foo

sleep 1

2.times do
  foo
end

We can even use foo inside iteration blocks or anywhere we may have written play or sample. This gives us a great way to express ourselves and to create new meaningful words for use in our compositions.

Functions are remembered across runs

So far, every time you've pressed the Run button, Sonic Pi has started from a completely blank slate. It knows nothing except for what is in the buffer. You can't reference code in another buffer or another thread. However, functions change that. When you define a function, Sonic Pi remembers it. Let's try it. Delete all the code in your buffer and replace it with:

foo

Press the Run button - and hear your function play. Where did the code go? How did Sonic Pi know what to play? Sonic Pi just remembered your function - so even after you deleted it from the buffer, it remembered what you had typed. This behaviour only works with functions created using define (and defonce).

Parameterised functions

You might be interested in knowing that just like you can pass min and max values to rrand, you can teach your functions to accept arguments. Let's take a look:

define :my_player do |n|
  play n
end

my_player 80
sleep 0.5
my_player 90

This isn't very exciting, but it illustrates the point. We've created our own version of play called my_player which is parameterised.

The parameters need to go after the do of the define do/end block, surrounded by vertical goalposts | and separated by commas ,. You may use any words you want for the parameter names.

The magic happens inside the define do/end block. You may use the parameter names as if they were real values. In this example I'm playing note n. You can consider the parameters as a kind of promise that when the code runs, they will be replaced with actual values. You do this by passing a parameter to the function when you call it. I do this with my_player 80 to play note 80. Inside the function definition, n is now replaced with 80, so play n turns into play 80. When I call it again with my_player 90, n is now replaced with 90, so play n turns into play 90.

Let's see a more interesting example:

define :chord_player do |root, repeats| 
  repeats.times do
    play chord(root, :minor), release: 0.3
    sleep 0.5
  end
end

chord_player :e3, 2
sleep 0.5
chord_player :a3, 3
chord_player :g3, 4
sleep 0.5
chord_player :e3, 3

Here I used repeats as if it was a number in the line repeats.times do. I also used root as if it was a note name in my call to play.

See how we're able to write something very expressive and easy to read by moving a lot of our logic into a function! 5.6 Variables

Variables

A useful thing to do in your code is to create names for things. Sonic Pi makes this very easy, you write the name you wish to use, an equal sign (=), then the thing you want to remember:

sample_name = :loop_amen

Here, we've 'remembered' the symbol :loop_amen in the variable sample_name. We can now use sample_name everywhere we might have used :loop_amen. For example:

sample_name = :loop_amen
sample sample_name

There are three main reasons for using variables in Sonic Pi: communicating meaning, managing repetition and capturing the results of things.

Communicating Meaning

When you write code it's easy to just think you're telling the computer how to do stuff - as long as the computer understands it's OK. However, it's important to remember that it's not just the computer that reads the code. Other people may read it too and try to understand what's going on. Also, you're likely to read your own code in the future and try to understand what's going on. Although it might seem obvious to you now - it might not be so obvious to others or even your future self!

One way to help others understand what your code is doing is to write comments (as we saw in a previous section). Another is to use meaningful variable names. Look at this code:

sleep 1.7533

Why does it use the number 1.7533? Where did this number come from? What does it mean? However, look at this code:

loop_amen_duration = 1.7533
sleep loop_amen_duration

Now, it's much clearer what 1.7533 means: it's the duration of the sample :loop_amen! Of course, you might say why not simply write:

sleep sample_duration(:loop_amen)

Which, of course, is a very nice way of communicating the intent of the code.

Managing Repetition

Often you see a lot of repetition in your code and when you want to change things, you have to change it in a lot of places. Take a look at this code:

sample :loop_amen
sleep sample_duration(:loop_amen)
sample :loop_amen, rate: 0.5
sleep sample_duration(:loop_amen, rate: 0.5)
sample :loop_amen
sleep sample_duration(:loop_amen)

We're doing a lot of things with :loop_amen! What if we wanted to hear what it sounded like with another loop sample such as :loop_garzul? We'd have to find and replace all :loop_amens with :loop_garzul. That might be fine if you have lots of time - but what if you're performing on stage? Sometimes you don't have the luxury of time - especially if you want to keep people dancing.

What if you'd written your code like this:

sample_name = :loop_amen
sample sample_name
sleep sample_duration(sample_name)
sample sample_name, rate: 0.5
sleep sample_duration(sample_name, rate: 0.5)
sample sample_name
sleep sample_duration(sample_name)

Now, that does exactly the same as above (try it). It also gives us the ability to just change one line sample_name = :loop_amen to sample_name = :loop_garzul and we change it in many places through the magic of variables.

Capturing Results

Finally, a good motivation for using variables is to capture the results of things. For example, you may wish to do things with the duration of a sample:

sd = sample_duration(:loop_amen)

We can now use sd anywhere we need the duration of the :loop_amen sample.

Perhaps more importantly, a variable allows us to capture the result of a call to play or sample:

s = play 50, release: 8

Now we have caught and remembered s as a variable, which allows us to control the synth as it is running:

s = play 50, release: 8
sleep 2
control s, note: 62

We'll look into controlling synths in more detail in a later section. 5.7 Thread Synchronisation

Thread Synchronisation

Once you have become sufficiently advanced live coding with a number of functions and threads simultaneously, you've probably noticed that it's pretty easy to make a mistake in one of the threads which kills it. That's no big deal, because you can easily restart the thread by hitting Run. However, when you restart the thread it is now out of time with the original threads.

Inherited Time

As we discussed earlier, new threads created with in_thread inherit all of the settings from the parent thread. This includes the current time. This means that threads are always in time with each other when started simultaneously.

However, when you start a thread on its own it starts with its own time which is unlikely to be in sync with any of the other currently running threads.

Cue and Sync

Sonic Pi provides a solution to this problem with the functions cue and sync.

cue allows us to send out heartbeat messages to all other threads. By default the other threads aren't interested and ignore these heartbeat messages. However, you can easily register interest with the sync function.

The important thing to be aware of is that sync is similar to sleep in that it stops the current thread from doing anything for a period of time. However, with sleep you specify how long you want to wait while with sync you don't know how long you will wait - as sync waits for the next cue from another thread which may be soon or a long time away.

Let's explore this in a little more detail:

in_thread do
  loop do
    cue :tick
    sleep 1
  end
end

in_thread do
  loop do
    sync :tick
    sample :drum_heavy_kick
  end
end

Here we have two threads - one acting like a metronome, not playing any sounds but sending out :tick heartbeat messages every beat. The second thread is synchronising on tick messages and when it receives one it inherits the time of the cue thread and continues running.

As a result, we will hear the :drum_heavy_kick sample exactly when the other thread sends the :tick message, even if the two threads didn't start their execution at the same time:

in_thread do
  loop do
    cue :tick
    sleep 1
  end
end

sleep(0.3)

in_thread do
  loop do
    sync :tick
    sample :drum_heavy_kick
  end
end

That naughty sleep call would typically make the second thread out of phase with the first. However, as we're using cue and sync, we automatically sync the threads bypassing any accidental timing offsets.

Cue Names

You are free to use whatever name you'd like for your cue messages - not just :tick. You just need to ensure that any other threads are syncing on the correct name - otherwise they'll be waiting for ever (or at least until you press the Stop button).

Let's play with a few cue names:

in_thread do
  loop do 
    cue [:foo, :bar, :baz].choose
    sleep 0.5
  end
end

in_thread do
  loop do 
    sync :foo 
    sample :elec_beep
  end
end

in_thread do
  loop do
    sync :bar
    sample :elec_flip
  end
end

in_thread do
  loop do
    sync :baz
    sample :elec_blup
  end
end

Here we have a main cue loop which is randomly sending one of the heartbeat names :foo, :bar or :baz. We then also have three loop threads syncing on each of those names independently and then playing a different sample. The net effect is that we hear a sound every 0.5 beats as each of the sync threads is randomly synced with the cue thread and plays its sample.

This of course also works if you order the threads in reverse as the sync threads will simply sit and wait for the next cue. 6 FX

Studio FX

One of the most rewarding and fun aspects of Sonic Pi is the ability to easily add studio effects to your sounds. For example, you may wish to add some reverb to parts of your piece, or some echo or perhaps even distort or wobble your basslines.

Sonic Pi provides a very simple yet powerful way of adding FX. It even allows you to chain them (so you can pass your sounds through distortion, then echo and then reverb) and also control each individual FX unit with opts (in a similar way to giving params to synths and samples). You can even modify the opts of the FX whilst it's still running. So, for example, you could increase the reverb on your bass throughout the track...

Guitar Pedals

If all of this sounds a bit complicated, don't worry. Once you play around with it a little, it will all become quite clear. Before you do though, a simple analogy is that of guitar FX pedals. There are many kinds of FX pedals you can buy. Some add reverb, others distort etc. A guitarist will plug his or her guitar into one FX pedal - i.e. distortion -, then take another cable and connect (chain) a reverb pedal. The output of the reverb pedal can then be plugged into the amplifier:

Guitar -> Distortion -> Reverb -> Amplifier

This is called FX chaining. Sonic Pi supports exactly this. Additionally, each pedal often has dials and sliders to allow you to control how much distortion, reverb, echo etc. to apply. Sonic Pi also supports this kind of control. Finally, you can imagine a guitarist playing whilst someone plays with the FX controls whilst they're playing. Sonic Pi also supports this - but instead of needing someone else to control things for you, that's where the computer steps in.

Let's explore FX! 6.1 Adding FX

Adding FX

In this section we'll look at a couple of FX: reverb and echo. We'll see how to use them, how to control their opts and how to chain them.

Sonic Pi's FX system uses blocks. So if you haven't read section 5.1 you might want to take a quick look and then head back.

Reverb

If we want to use reverb we write with_fx :reverb as the special code to our block like this:

with_fx :reverb do
  play 50
  sleep 0.5
  sample :elec_plip
  sleep 0.5
  play 62
end

Now play this code and you'll hear it played with reverb. It sounds good, doesn't it! Everything sounds pretty nice with reverb.

Now let's look what happens if we have code outside the do/end block:

with_fx :reverb do
  play 50
  sleep 0.5
  sample :elec_plip
  sleep 0.5
  play 62
end

sleep 1
play 55

Notice how the final play 55 isn't played with reverb. This is because it is outside the do/end block, so it isn't captured by the reverb FX.

Similarly, if you make sounds before the do/end block, they also won't be captured:

play 55
sleep 1

with_fx :reverb do
  play 50
  sleep 0.5
  sample :elec_plip
  sleep 0.5
  play 62
end

sleep 1
play 55

Echo

There are many FX to choose from. How about some echo?

with_fx :echo do
  play 50
  sleep 0.5
  sample :elec_plip
  sleep 0.5
  play 62
end

One of the powerful aspects of Sonic Pi's FX blocks is that they may be passed parameters similar to parameters we've already seen with play and sample. For example a fun echo parameter to play with is phase: which represents the duration of a given echo in beats. Let's make the echo slower:

with_fx :echo, phase: 0.5 do
  play 50
  sleep 0.5
  sample :elec_plip
  sleep 0.5
  play 62
end

Let's also make the echo faster:

with_fx :echo, phase: 0.125 do
  play 50
  sleep 0.5
  sample :elec_plip
  sleep 0.5
  play 62
end

Let's make the echo take longer to fade away by setting the decay: time to 8 beats:

with_fx :echo, phase: 0.5, decay: 8 do
  play 50
  sleep 0.5
  sample :elec_plip
  sleep 0.5
  play 62
end

Nesting FX

One of the most powerful aspects of the FX blocks is that you can nest them. This allows you to very easily chain FX together. For example, what if you wanted to play some code with echo and then with reverb? Easy, just put one inside the other:

with_fx :reverb do
  with_fx :echo, phase: 0.5, decay: 8 do
    play 50
    sleep 0.5
    sample :elec_blup
    sleep 0.5
    play 62
  end
end

Think about the audio flowing from the inside out. The sound of all the code within the inner do/end block such as play 50 is first sent to the echo FX and the sound of the echo FX is in turn sent out to the reverb FX.

We may use very deep nestings for crazy results. However, be warned, the FX can use a lot of resources and when you nest them you're effectively running multiple FX simultaneously. So be sparing with your use of FX especially on low powered platforms such as the Raspberry Pi.

Discovering FX

Sonic Pi ships with a large number of FX for you to play with. To find out which ones are available, click on FX in the far left of this help system and you'll see a list of available options. Here's a list of some of my favourites:

• wobble,
• reverb,
• echo,
• distortion,
• slicer

Now go crazy and add FX everywhere for some amazing new sounds! 6.2 FX in Practice

FX in Practice

Although they look deceptively simple on the outside, FX are actually quite complex beasts internally. Their simplicity often entices people to overuse them in their pieces. This may be fine if you have a powerful machine, but if - like me - you use a Raspberry Pi to jam with, you need to be careful about how much work you ask it to do if you want to ensure the beats keep flowing.

Consider this code:

loop do
  with_fx :reverb do
    play 60, release: 0.1
    sleep 0.125
  end
end

In this code we're playing note 60 with a very short release time, so it's a short note. We also want reverb so we've wrapped it in a reverb block. All good so far. Except...

Let's look at what the code does. First we have a loop which means everything inside of it is repeated forever. Next we have a with_fx block. This means we will create a new reverb FX every time we loop. This is like having a separate FX reverb pedal for every time you pluck a string on a guitar. It's cool that you can do this, but it's not always what you want. For example, this code will struggle to run nicely on a Raspberry Pi. All the work of creating the reverb and then waiting until it needs to be stopped and removed is all handled by with_fx for you, but this takes CPU power which may be precious.

How do we make it more similar to a traditional setup where our guitarist has just one reverb pedal which all sounds pass through? Simple:

with_fx :reverb do
  loop do
    play 60, release: 0.1
    sleep 0.125
  end
end

We put our loop inside the with_fx block. This way we only create a single reverb for all notes played in our loop. This code is a lot more efficient and would work fine on a Raspberry Pi.

A compromise is to use with_fx over an iteration within a loop:

loop do
  with_fx :reverb do
    16.times do
      play 60, release: 0.1
      sleep 0.125
    end
  end
end

This way we've lifted the with_fx out of the inner part of the loop and we're now creating a new reverb every 16 notes.

Remember, there are no mistakes, just possibilities. However, each of these approaches will have a different sound and also different performance characteristics. So play around and use the approach that sounds best to you whilst also working within the performance constraints of your platform. 7 Control

Controlling running sounds

So far we've looked at how you can trigger synths and samples, and also how to change their default opts such as amplitude, pan, envelope settings and more. Each sound triggered is essentially its own sound with its own list of options set for the duration of the sound.

Wouldn't it also be cool if you could change a sound's opts whilst it's still playing, just like you might bend a string of a guitar whilst it's still vibrating?

You're in luck - this section will show you how to do exactly this. 7.1 Controlling Running Synths

Controlling Running Synths

So far we've only concerned ourselves with triggering new sounds and FX. However, Sonic Pi gives us the ability to manipulate and control currently running sounds. We do this by using a variable to capture a reference to a synth:

s = play 60, release: 5

Here, we have a run-local variable s which represents the synth playing note 60. Note that this is run-local - you can't access it from other runs like functions.

Once we have s, we can start controlling it via the control function:

s = play 60, release: 5
sleep 0.5
control s, note: 65
sleep 0.5
control s, note: 67
sleep 3
control s, note: 72

The thing to notice is that we're not triggering 4 different synths here

• we're just triggering one synth and then change the pitch 3 times afterwards, while it's playing.

We can pass any of the standard opts to control, so you can control things like amp:, cutoff: or pan:.

Non-controllable Options

Some of the opts can't be controlled once the synth has started. This is the case for all the ADSR envelope parameters. You can find out which opts are controllable by looking at their documentation in the help system. If the documentation says Can not be changed once set, you know it's not possible to control the opt after the synth has started. 7.2 Controlling FX

Controlling FX

It is also possible to control FX, although this is achieved in a slightly different way:

with_fx :reverb do |r|
  play 50
  sleep 0.5
  control r, mix: 0.7
  play 55
  sleep 1
  control r, mix: 0.9
  sleep 1
  play 62
end

Instead of using a variable, we use the goalpost parameters of the do/end block. Inside the | bars, we need to specify a unique name for our running FX which we then reference from the containing do/end block. This behaviour is identical to using parameterised functions.

Now go and control some synths and FX! 7.3 Sliding Options

Sliding Opts

Whilst exploring the synth and FX opts, you might have noticed that there are a number of opts ending with _slide. You might have even tried calling them and seeing no effect. This is because they're not normal parameters, they're special opts that only work when you control synths as introduced in the previous section.

Consider the following example:

s = play 60, release: 5
sleep 0.5
control s, note: 65
sleep 0.5
control s, note: 67
sleep 3
control s, note: 72

Here, you can hear the synth pitch changing immediately on each control call. However, we might want the pitch to slide between changes. As we're controlling the note: parameter, to add slide, we need to set the note_slide parameter of the synth:

s = play 60, release: 5, note_slide: 1
sleep 0.5
control s, note: 65
sleep 0.5
control s, note: 67
sleep 3
control s, note: 72

Now we hear the notes being bent between the control calls. It sounds nice, doesn't it? You can speed up the slide by using a shorter time such as note_slide: 0.2 or slow it down by using a longer slide time.

Every parameter that can be controlled has a corresponding _slide parameter for you to play with.

Sliding is sticky

Once you've set a _slide parameter on a running synth, it will be remembered and used every time you slide the corresponding parameter. To stop sliding you must set the _slide value to 0 before the next control call.

Sliding FX Opts

It is also possible to slide FX opts:

with_fx :wobble, phase: 1, phase_slide: 5 do |e|
  use_synth :dsaw
  play 50, release: 5
  control e, phase: 0.025
end

Now have fun sliding things around for smooth transitions and flowing control... 8 Data Structures

Data Structures

A very useful tool in a programmer's toolkit is a data structure.

Sometimes you may wish to represent and use more than one thing. For example, you may find it useful to have a series of notes to play one after another. Programming languages have data structures to allow you do exactly this.

There are many exciting and exotic data structures available to programmers - and people are always inventing new ones. However, for now we only really need to consider a very simple data structure - the list.

Let's look at it in more detail. We'll cover its basic form and then also how lists can be used to represent scales and chords. 8.1 Lists

Lists

In this section we'll take a look at a data structure which is very useful - the list. We met it very briefly before in the section on randomisation when we randomly chose from a list of notes to play:

play choose([50, 55, 62])

In this section we'll explore using lists to also represent chords and scales. First let's recap how we might play a chord. Remember that if we don't use sleep, sounds all happen at the same time:

play 52
play 55
play 59

Let's look at other ways to represent this code.

Playing a List

One option is to place all the notes in a list: [52, 55, 59]. Our friendly play function is smart enough to know how to play a list of notes. Try it:

play [52, 55, 59]

Ooh, that's already nicer to read. Playing a list of notes doesn't stop you from using any of the parameters as normal:

play [52, 55, 59], amp: 0.3

Of course, you can also use the traditional note names instead of the MIDI numbers:

play [:E3, :G3, :B3]

Now those of you lucky enough to have studied some music theory might recognise that chord as E Minor played in the 3rd octave.

Accessing a List

Another very useful feature of a list is the ability to get information out of it. This may sound a bit strange, but it's no more complicated than someone asking you to turn a book to page 23. With a list, you'd say, what's the element at index 23? The only strange thing is that in programming indexes usually start at 0 not 1.

With list indexes we don't count 1, 2, 3... Instead we count 0, 1, 2...

Let's look at this in a little more detail. Take a look at this list:

[52, 55, 59]

There's nothing especially scary about this. Now, what's the second element in that list? Yes, of course, it's 55. That was easy. Let's see if we can get the computer to answer it for us too:

puts [52, 55, 59][1]

OK, that looks a bit weird if you've never seen anything like it before. Trust me though, it's not too hard. There are three parts to the line above: the word puts , our list 52, 55, 59 and our index [1]. Firstly we're saying puts because we want Sonic Pi to print the answer out for us in the log. Next, we're giving it our list, and finally our index is asking for the second element. We need to surround our index with square brackets and because counting starts at 0, the index for the second element is 1. Look:

# indexes:  0   1   2
           [52, 55, 59]

Try running the code puts [52, 55, 59][1] and you'll see 55 pop up in the log. Change the index 1 to other indexes, try longer lists and think about how you might use a list in your next code jam. For example, what musical structures might be represented as a series of numbers...

8.2 Chords

Chords

Sonic Pi has built-in support for chord names which will return lists. Try it for yourself:

play chord(:E3, :minor)

Now, we're really getting somewhere. That looks a lot more pretty than the raw lists (and is easier to read for other people). So what other chords does Sonic Pi support? Well, a lot. Try some of these:

• chord(:E3, :m7)
• chord(:E3, :minor)
• chord(:E3, :dim7)
• chord(:E3, :dom7)

Arpeggios

We can easily turn chords into arpeggios with the function play_pattern:

play_pattern chord(:E3, :m7)

Ok, that's not so fun - it played it really slowly. play_pattern will play each note in the list separated with a call to sleep 1 between each call to play. We can use another function play_pattern_timed to specify our own timings and speed things up:

play_pattern_timed chord(:E3, :m7), 0.25

We can even pass a list of times which it will treat as a circle of times:

play_pattern_timed chord(:E3, :m13), [0.25, 0.5]

This is the equivalent to:

play 52
sleep 0.25
play 55
sleep 0.5
play 59
sleep 0.25
play 62
sleep 0.5
play 66
sleep 0.25
play 69
sleep 0.5
play 73

Which would you prefer to write? 8.3 Scales

Scales

Sonic Pi has support for a wide range of scales. How about playing a C3 major scale?

play_pattern_timed scale(:c3, :major), 0.125, release: 0.1

We can even ask for more octaves:

play_pattern_timed scale(:c3, :major, num_octaves: 3), 0.125, release: 0.1

How about all the notes in a pentatonic scale?

play_pattern_timed scale(:c3, :major_pentatonic, num_octaves: 3), 0.125, release: 0.1

Random notes

Chords and scales are great ways of constraining a random choice to something meaningful. Have a play with this example which picks random notes from the chord E3 minor:

use_synth :tb303
loop do
  play choose(chord(:E3, :minor)), release: 0.3, cutoff: rrand(60, 120)
  sleep 0.25
end

Try switching in different chord names and cutoff ranges.

Discovering Chords and Scales

To find out which scales and chords are supported by Sonic Pi simply click the Lang button on the far left of this tutorial and then choose either chord or scale in the API list. In the information in the main panel, scroll down until you see a long list of chords or scales (depending on which you're looking at).

Have fun and remember: there are no mistakes, only opportunities. 8.4 Rings

Rings

An interesting spin on standard lists are rings. If you know some programming, you might have come across ring buffers or ring arrays. Here, we'll just go for ring - it's short and simple.

In the previous section on lists we saw how we could fetch elements out of them by using the indexing mechanism:

puts [52, 55, 59][1]

Now, what happens if you want index 100? Well, there's clearly no element at index 100 as the list has only three elements in it. So Sonic Pi will return you nil which means nothing.

However, consider you have a counter such as the current beat which continually increases. Let's create our counter and our list:

counter = 0
notes = [52, 55, 59]

We can now use our counter to access a note in our list:

puts notes[counter]

Great, we got 52. Now, let's increment our counter and get another note:

counter = (inc counter)
puts notes[counter]

Super, we now get 55 and if we do it again we get 59. However, if we do it again, we'll run out of numbers in our list and get nil. What if we wanted to just loop back round and start at the beginning of the list again? This is what rings are for.

Creating Rings

We can create rings one of two ways. Either we use the ring function with the elements of the ring as parameters:

(ring 52, 55, 59)

Or we can take a normal list and convert it to a ring by sending it the .ring message:

[52, 55, 59].ring

Indexing Rings

Once we have a ring, you can use it in exactly the same way you would use a normal list with the exception that you can use indexes that are negative or larger than the size of the ring and they'll wrap round to always point at one of the ring's elements:

(ring 52, 55, 59)[0] #=> 52
(ring 52, 55, 59)[1] #=> 55
(ring 52, 55, 59)[2] #=> 59
(ring 52, 55, 59)[3] #=> 52
(ring 52, 55, 59)[-1] #=> 59

Using Rings

Let's say we're using a variable to represent the current beat number. We can use this as an index into our ring to fetch notes to play, or release times or anything useful we've stored in our ring regardless of the beat number we're currently on.

Scales and Chords are Rings

A useful thing to know is that the lists returned by scale and chord are also rings and allow you to access them with arbitrary indexes.

Ring Constructors

In addition to ring there are a number of other functions which will construct a ring for us.

• range invites you specify a starting point, end point and step size.
• bools allows you to use 1s and 0s to succinctly represent booleans.
• knit allows you to knit a sequence of repeated values.
• spread creates a ring of bools with a Euclidean distribution.

Take a look at their respective documentation for more information.

9 Live Coding

Live Coding

One of the most exciting aspects of Sonic Pi is that it enables you to write and modify code live to make music, just like you might perform live with a guitar. One advantage of this approach is to give you more feedback whilst composing (get a simple loop running and keep tweaking it till it sounds just perfect). However, the main advantage is that you can take Sonic Pi on stage and gig with it.

In this section we'll cover the fundamentals of turning your static code compositions into dynamic performances.

Hold on to your seats... 9.1 Live Coding Fundamentals

Live Coding

Now we've learned enough to really start having some fun. In this section we'll draw from all the previous sections and show you how you can start making your music compositions live and turning them into a performance. For that we'll need 3 main ingredients:

• An ability to write code that makes sounds - CHECK!
• An ability to write functions - CHECK!
• An ability to use (named) threads - CHECK!

Alrighty, let's get started. Let's live code our first sounds. We first need a function containing the code we want to play. Let's start simple. We also want to loop calls to that function in a thread:

define :my_loop do
  play 50
  sleep 1
end

in_thread(name: :looper) do
  loop do
    my_loop
  end
end

If that looks a little too complicated to you, go back and re-read the sections on functions and threads. It's not too complicated if you've already wrapped your head around these things.

What we have here is a function definition which just plays note 50 and sleeps for a beat. We then define a named thread called :looper which just loops around calling my_loop repeatedly.

If you run this code, you'll hear note 50 repeating again and again...

Changing it up

Now, this is where the fun starts. Whilst the code is still running change 50 to another number, say 55, then press the Run button again. Woah! It changed! Live!

It didn't add a new layer because we're using named threads which only allow one thread for each name. Also, the sound changed because we redefined the function. We gave :my_loop a new definition. When the :looper thread looped around it simply called the new definition.

Try changing it again, change the note, change the sleep time. How about adding a use_synth statement? For example, change it to:

define :my_loop do
  use_synth :tb303
  play 50, release: 0.3
  sleep 0.25
end

Now it sounds pretty interesting, but we can spice it up further. Instead of playing the same note again and again, try playing a chord:

define :my_loop do
  use_synth :tb303
  play chord(:e3, :minor), release: 0.3
  sleep 0.5
end

How about playing random notes from the chord:

define :my_loop do
  use_synth :tb303
  play choose(chord(:e3, :minor)), release: 0.3
  sleep 0.25
end

Or using a random cutoff value:

define :my_loop do
  use_synth :tb303
  play choose(chord(:e3, :minor)), release: 0.2, cutoff: rrand(60, 130)
  sleep 0.25
end

Finally, add some drums:

define :my_loop do
  use_synth :tb303
  sample :drum_bass_hard, rate: rrand(0.5, 2)
  play choose(chord(:e3, :minor)), release: 0.2, cutoff: rrand(60, 130)
  sleep 0.25
end

Now things are getting exciting!

However, before you jump up and start live coding with functions and threads, stop what you're doing and read the next section on live_loop which will change the way you code in Sonic Pi forever... 9.2 Live Loops

Live Loops

Ok, so this section of the tutorial is the real gem. If you only read one section, it should be this one. If you read the previous section on Live Coding Fundamentals, live_loop is a simple way of doing exactly that but without having to write so much.

If you didn't read the previous section, live_loop is the best way to jam with Sonic Pi.

Let's play. Write the following in a new buffer:

live_loop :foo do
  play 60
  sleep 1
end

Now press the Run button. You hear a basic beep every beat. Nothing fun there. However, don't press Stop just yet. Change the 60 to 65 and press Run again.

Woah! It changed automatically without missing a beat. This is live coding.

Why not change it to be more bass like? Just update your code whilst it's playing:

live_loop :foo do
  use_synth :prophet
  play :e1, release: 8
  sleep 8
end

Then hit Run.

Let's make the cutoff move around:

live_loop :foo do
  use_synth :prophet
  play :e1, release: 8, cutoff: rrand(70, 130)
  sleep 8
end

Hit Run again.

Add some drums:

live_loop :foo do
  sample :loop_garzul
  use_synth :prophet
  play :e1, release: 8, cutoff: rrand(70, 130)
  sleep 8
end

Change the note from e1 to c1:

live_loop :foo do
  sample :loop_garzul
  use_synth :prophet
  play :c1, release: 8, cutoff: rrand(70, 130)
  sleep 8
end

Now stop listening to me and play around yourself! Have fun! 9.3 Multiple Live Loops

Multiple Live Loops

Consider the following live loop:

live_loop :foo do
  play 50
  sleep 1
end

You may have wondered why it needs the name :foo. This name is important because it signifies that this live loop is different from all other live loops.

There can never be two live loops running with the same name.

This means that if we want multiple concurrently running live loops, we just need to give them different names:

live_loop :foo do
  use_synth :prophet
  play :c1, release: 8, cutoff: rrand(70, 130)
  sleep 8
end

live_loop :bar do
  sample :bd_haus
  sleep 0.5
end

You can now update and change each live loop independently and it all just works.

Syncing Live Loops

One thing you might have already noticed is that live loops work automatically with the thread cue mechanism we explored previously. Every time the live loop loops, it generates a new cue event with the name of the live loop. We can therefore sync on these cues to ensure our loops are in sync without having to stop anything.

Consider this badly synced code:

live_loop :foo do
  play :e4, release: 0.5
  sleep 0.4
end

live_loop :bar do
  sample :bd_haus
  sleep 1
end

Let's see if we can fix the timing and sync without stopping it. First, let's fix the :foo loop to make the sleep a factor of 1 - something like 0.5 will do:

live_loop :foo do
  play :e4, release: 0.5
  sleep 0.5
end

live_loop :bar do
  sample :bd_haus
  sleep 1
end

We're not quite finished yet though - you'll notice that the beats don't quite line up correctly. This is because the loops are out of phase. Let's fix that by syncing one to the other:

live_loop :foo do
  play :e4, release: 0.5
  sleep 0.5
end

live_loop :bar do
  sync :foo
  sample :bd_haus
  sleep 1
end

Wow, everything is now perfectly in time - all without stopping.

Now, go forth and live code with live loops! 9.4 Ticking

Ticking

Something you'll likely find yourself doing a lot when live coding is looping through rings. You'll be putting notes into rings for melodies, sleeps for rhythms, chord progressions, timbral variations, etc. etc.

Ticking Rings

Sonic Pi provides a very handy tool for working with rings within live_loops. It's called the tick system. It provides you with the ability to tick through rings. Let's look at an example:

live_loop :arp do
  play (scale :e3, :minor_pentatonic).tick, release: 0.1
  sleep 0.125
end

Here, we're just grabbing the scale E3 minor pentatonic and ticking through each element. This is done by adding .tick to the end of the scale declaration. This tick is local to the live loop, so each live loop can have its own independent tick:

live_loop :arp do
  play (scale :e3, :minor_pentatonic).tick, release: 0.1
  sleep 0.125
end

live_loop :arp2 do
  use_synth :dsaw
  play (scale :e2, :minor_pentatonic, num_octaves: 3).tick, release: 0.25
  sleep 0.25
end

Tick

You can also call tick as a standard fn and use the value as an index:

live_loop :arp do
  idx = tick
  play (scale :e3, :minor_pentatonic)[idx], release: 0.1
  sleep 0.125
end

However, it is much nicer to call .tick at the end. The tick fn is for when you want to do fancy things with the tick value and for when you want to use ticks for other things than indexing into rings.

Look

The magical thing about tick is that not only does it return a new index (or the value of the ring at that index) it also makes sure that next time you call tick, it's the next value. Take a look at the examples in the docs for tick for many ways of working with this. However, for now, it's important to point out that sometimes you'll want to just look at the current tick value and not increase it. This is available via the look fn. You can call look as a standard fn or by adding .look to the end of a ring.

Naming Ticks

Finally, sometimes you'll need more than one tick per live loop. This is achieved by giving your tick a name:

live_loop :arp do
  play (scale :e3, :minor_pentatonic).tick(:foo), release: 0.1
  sleep (ring 0.125, 0.25).tick(:bar)
end

Here we're using two ticks one for the note to play and another for the sleep time. As they're both in the same live loop, to keep them separate we need to give them unique names. This is exactly the same kind of thing as naming live_loops - we just pass a symbol prefixed with a :. In the example above we called one tick :foo and the other :bar. If we want to look at these we also need to pass the name of the tick to look.

Don't make it too complicated

Most of the power in the tick system isn't useful when you get started. Don't try and learn everything in this section. Just focus on ticking through a single ring. That'll give you most of the joy and simplicity of ticking through rings in your live_loops.

Take a look at the documentation for tick where there are many useful examples and happy ticking!

10 Essential Knowledge

Essential Knowledge

This section will cover some very useful - in fact essential - knowledge for getting the most out of your Sonic Pi experience.

We'll cover how to take advantage of the many keyboard shortcuts available to you, how to share your work and some tips on performing with Sonic Pi. 10.1 Using Shortcuts

Using Shortcuts

Sonic Pi is as much an instrument as a coding environment. Shortcuts can therefore make playing Sonic Pi much more efficient and natural - especially when you're playing live in front of an audience.

Much of Sonic Pi can be controlled through the keyboard. As you gain more familiarity working and performing with Sonic Pi, you'll likely start using the shortcuts more and more. I personally touch-type (I recommend you consider learning too) and find myself frustrated whenever I need to reach for the mouse as it slows me down. I therefore use all of these shortcuts on a very regular basis!

Therefore, if you learn the shortcuts, you'll learn to use your keyboard effectively and you'll be live coding like a pro in no time.

However, don't try and learn them all at once, just try and remember the ones you use most and then keep adding more to your practice.

Consistency across Platforms

Imagine you're learning the clarinet. You'd expect all clarinets of all makes to have similar controls and fingerings. If they didn't, you'd have a tough time switching between different clarinets and you'd be stuck to using just one make.

Unfortunately the three major operating systems (Linux, Mac OS X and Windows) come with their own standard defaults for actions such as cut and paste etc. Sonic Pi will try and honour these standards. However priority is placed on consistency across platforms within Sonic Pi rather than attempting to conform to a given platform's standards. This means that when you learn the shortcuts whilst playing with Sonic Pi on your Raspberry Pi, you can move to the Mac or PC and feel right at home.

Control and Meta

Part of the notion of consistency is the naming of shortcuts. In Sonic Pi we use the names Control and Meta to refer to the two main combination keys. On all platforms Control is the same. However, on Linux and Windows, Meta is actually the Alt key while on Mac Meta is the Command key. For consistency we'll use the term Meta - just remember to map that to the appropriate key on your operating system.

Abbreviations

To help keep things simple and readable, we'll use the abbreviations C- for Control plus another key and M- for Meta plus another key. For example, if a shortcut requires you to hold down both Meta and r we'll write that as M-r. The - just means "at the same time as."

The following are some of the shortcuts I find most useful.

Stopping and starting

Instead of always reaching for the mouse to run your code, you can simply press M-r. Similarly, to stop running code you can press M-s.

Navigation

I'm really lost without the navigation shortcuts. I therefore highly recommend you spend the time to learn them. These shortcuts also work extremely well when you've learned to touch type as they use the standard letters rather than requiring you to move your hand to the mouse or the arrow keys on your keyboard.

You can move to the beginning of the line with C-a, the end of the line with C-e, up a line with C-p, down a line with C-n, forward a character with C-f, and back a character with C-b. You can even delete all the characters from the cursor to the end of the line with C-k.

Tidy Code

To auto-align your code simply press M-m.

Help System

To toggle the help system you can press M-i. However, a much more useful shortcut to know is C-i which will look up the word underneath the cursor and display the docs if it finds anything. Instant help!

For a full list take a look at section 10.2 Shortcut Cheatsheet. 10.2 Shortcut Cheatsheet

Shortcut Cheatsheet

The following is a summary of the main shortcuts available within Sonic Pi. Please see Section 10.1 for motivation and background.

Conventions

In this list, we use the following conventions (where Meta is one of Alt on Windows/Linux or Cmd on Mac):

• C-a means hold the Control key then press the a key whilst holding them both at the same time, then releasing.
• M-r means hold the Meta key and then press the r key whilst holding them both at the same time, then releasing.
• S-M-z means hold the Shift key, then the Meta key, then finally the z key all at the same time, then releasing.
• C-M-f means hold the Control key, then press Meta key, finally the f key all at the same time, then releasing.

Main Application Manipulation

• M-r - Run code
• M-s - Stop code
• M-i - Toggle Help System
• M-p - Toggle Preferences
• M-< - Switch buffer to the left
• M-> - Switch buffer to the right
• M-+ - Increase text size of current buffer
• M-- - Decrease text size of current buffer

Selection/Copy/Paste

• M-a - Select all
• M-c - Copy selection to paste buffer
• M-] - Copy selection to paste buffer
• M-x - Cut selection to paste buffer
• C-] - Cut selection to paste buffer
• C-k - Cut to the end of the line
• M-v - Paste from paste buffer to editor
• C-y - Paste from paste buffer to editor
• C-SPACE - Set mark. Navigation will now manipulate highlighted region. Use C-g to escape.

Text Manipulation

• M-m - Align all text
• Tab - Align current line/selection (or complete list)
• C-l - Centre editor
• M-/ - Comment/Uncomment current line
• C-t - Transpose/swap characters
• M-u - Convert next word (or selection) to upper case.
• M-l - Convert next word (or selection) to lower case.

Navigation

• C-a - Move to beginning of line
• C-e - Move to end of line
• C-p - Move to previous line
• C-n - Move to next line
• C-f - Move forward one character
• C-b - Move backward one character
• M-f - Move forward one word
• M-b - Move backward one word
• C-M-n - Move line or selection down
• C-M-p - Move line or selection up
• S-M-u - Move up 10 lines
• S-M-d - Move down 10 lines

Deletion

• C-h - Delete previous character
• C-d - Delete next character

Advanced Editor Features

• C-i - Show docs for word under cursor
• M-z - Undo
• S-M-z - Redo
• C-g - Escape
• S-M-f - Toggle fullscreen mode
• S-M-b - Toggle visibility of buttons
• S-M-l - Toggle visibility of log
• S-M-m - Toggle between light/dark modes

10.3 Sharing

Sharing

Sonic Pi is all about sharing and learning with each other.

Once you've learned how to code music, sharing your compositions is as simple as sending an email containing your code. Please do share your code with others so they can learn from your work and even use parts in a new mash-up.

If you're unsure of the best way to share your work with others I recommend putting your code on GitHub and your music on SoundCloud. That way you'll be able to easily reach a large audience.

Code -> GitHub

GitHub is a site for sharing and working with code. It's used by professional developers as well as artists for sharing and collaborating with code. The simplest way to share a new piece of code (or even an unfinished piece) is to create a Gist. A Gist is a simple way of uploading your code in a simple way that others can see, copy and share.

Audio -> SoundCloud

Another important way of sharing your work is to record the audio and upload it to SoundCloud. Once you've uploaded your piece, other users can comment and discuss your work. I also recommend placing a link to a Gist of your code in the track description.

To record your work, hit the Rec button in the toolbar, and recording starts immediately. Hit Run to start your code if it isn't already in progress. When you're done recording, press the flashing Rec button again, and you'll be prompted to enter a filename. The recording will be saved as a WAV file, which can be edited and converted to MP3 by any number of free programs (try Audacity for instance).

Hope

I encourage you to share your work and really hope that we'll all teach each other new tricks and moves with Sonic Pi. I'm really excited by what you'll have to show me. 10.4 Performing

Performing

One of the most exciting aspects of Sonic Pi is that it enables you to use code as a musical instrument. This means that writing code live can now be seen as a new way of performing music.

We call this Live Coding.

Show Your Screen

When you live code I recommend you show your screen to your audience. Otherwise it's like playing a guitar but hiding your fingers and the strings. When I practice at home I use a Raspberry Pi and a little mini projector on my living room wall. You could use your TV or one of your school/work projectors to give a show. Try it, it's a lot of fun.

Form a Band

Don't just play on your own - form a live coding band! It's a lot of fun jamming with others. One person could do beats, another ambient background, etc. See what interesting combinations of sounds you can have together.

TOPLAP

Live coding isn't completely new - a small number of people have been doing it for a few years now, typically using bespoke systems they've built for themselves. A great place to go and find out more about other live coders and systems is TOPLAP.

Algorave

Another great resource for exploring the live coding world is Algorave. Here you can find all about a specific strand of live coding for making music in nightclubs. 11 Minecraft Pi

Minecraft Pi

Sonic Pi now supports a simple API for interacting with Minecraft Pi - the special edition of Minecraft which is installed by default on the Raspberry Pi's Raspbian Linux-based operating system.

No need to import libraries

The Minecraft Pi integration has been designed to be insanely easy to use. All you need to do is to launch a Minecraft Pi and create a world. You're then free to use the mc_* fns just like you might use play and synth. There's no need to import anything or install any libraries - it's all ready to go and works out of the box.

Automatic Connection

The Minecraft Pi API takes care of managing your connection to the Minecraft Pi application. This means you don't need to worry about a thing. If you try and use the Minecraft Pi API when Minecraft Pi isn't open, Sonic Pi will politely tell you. Similarly, if you close Minecraft Pi whilst you're still running a live_loop that uses the API, the live loop will stop and politely tell you that it can't connect. To reconnect, just launch Minecraft Pi again and Sonic Pi will automatically detect and re-create the connection for you.

Designed to be Live Coded

The Minecraft Pi API has been designed to work seamlessly within live_loops. This means it's possible to synchronise modifications in your Minecraft Pi worlds with modifications in your Sonic Pi sounds. Instant Minecraft-based music videos! Note however that Minecraft Pi is alpha software and is known to be slightly buggy. If you encounter any problems simply restart Minecraft Pi and carry on as before. Sonic Pi's automatic connection functionality will take care of things for you.

Requires a Raspberry Pi 2.0

It is highly recommended that you use a Raspberry Pi 2 if you wish to run both Sonic Pi and Minecraft at the same time - especially if you want to use Sonic Pi's sound capabilities.

API Support

At this stage, Sonic Pi supports basic block and player manipulations which are detailed in Section 11.1. Support for event callbacks triggered by player interactions in the world is planned for a future release. 11.1 Basic API

Basic Minecraft Pi API

Sonic Pi currently supports the following basic interactions with Minecraft Pi:

• Displaying chat messages
• Setting the position of the user
• Getting the position of the user
• Setting the block type at a given coordinate
• Getting the block type at a given coordinate

Let's look at each of these in turn.

Displaying chat messages

Let's see just how easy it is to control Minecraft Pi from Sonic Pi. First, make sure you have both Minecraft Pi and Sonic Pi open at the same time and also make sure you've entered a Minecraft world and can walk around.

In a fresh Sonic Pi buffer simply enter the following code:

mc_message "Hello from Sonic Pi"

When you hit the Run button, you'll see your message flash up on the Minecraft window. Congratulations, you've written your first Minecraft code! That was easy wasn't it.

Setting the position of the user

Now, let's try a little magic. Let's teleport ourselves somewhere! Try the following:

mc_teleport 50, 50, 50

When you hit Run - boom! You're instantantly transported to a new place. Most likely it was somewhere in the sky and you fell down either to dry land or into water. Now, what are those numbers: 50, 50, 50? They're the coordinates of the location you're trying to teleport to. Let's take a brief moment to explore what coordinates are and how they work because they're really, really important for programming Minecraft.

Coordinates

Imagine a pirate's map with a big X marking the location of some treasure. The exact location of the X can be described with two numbers - how far along the map from left to right and how far along the map from bottom to top. For example 10cm across and 8cm up. These two numbers 10 and 8 are coordinates. You could easily imagine describing the locations of other stashes of treasure with other pairs of numbers. Perhaps there's a big chest of gold at 2 across and 9 up...

Now, in Minecraft two numbers isn't quite enough. We also need to know how high we are. We therefore need three numbers:

• How far from right to left in the world - x
• How far from front to back in the world - z
• How high up we are in the world - y One more thing - we typically describe these coordinates in this order x, y, z.

Finding your current coordinates

Let's have a play with coordinates. Navigate to a nice place in the Minecraft map and then switch over to Sonic Pi. Now enter the following:

puts mc_location

When you hit the Run button you'll see the coordinates of your current position displayed in the log window. Take a note of them, then move forward in the world and try again. Notice how the coordinates changed! Now, I recommend you spend some time repeating exactly this - move a bit in the world, take a look at the coordinates and repeat. Do this until you start to get a feel for how the coordinates change when you move. Once you've understood how coordinates work, programming with the Minecraft API will be a complete breeze.

Let's Build!

Now that you know how to find the current position and to teleport using coordinates, you have all the tools you need to start building things in Minecraft with code. Let's say you want to make the block with coordinates 40, 50, 60 to be glass. That's super easy:

mc_set_block :glass, 40, 50, 60

Haha, it really was that easy. To see your handywork just teleport nearby and take a look:

mc_teleport 35, 50, 60

Now turn around and you should see your glass block! Try changing it to diamond:

mc_set_block :diamond, 40, 50, 60

If you were looking in the right direction you might have even seen it change in front of your eyes! This is the start of something exciting...

Looking at blocks

Let's look at one last thing before we move onto something a bit more involved. Given a set of coordinates we can ask Minecraft what the type of a specific block is. Let's try it with the diamond block you just created:

puts mc_get_block 40, 50, 60

Yey! It's :diamond. Try changing it back to glass and asking again - does it now say :glass? I'm sure it does :-)

Available block types

Before you go on a Minecraft Pi coding rampage, you might find this list of available block types useful:

    :air
    :stone
    :grass
    :dirt
    :cobblestone
    :wood_plank
    :sapling
    :bedrock
    :water_flowing
    :water
    :water_stationary
    :lava_flowing
    :lava
    :lava_stationary
    :sand
    :gravel
    :gold_ore
    :iron_ore
    :coal_ore
    :wood
    :leaves
    :glass
    :lapis
    :lapis_lazuli_block
    :sandstone
    :bed
    :cobweb
    :grass_tall
    :flower_yellow
    :flower_cyan
    :mushroom_brown
    :mushroom_red
    :gold_block
    :gold
    :iron_block
    :iron
    :stone_slab_double
    :stone_slab
    :brick
    :brick_block
    :tnt
    :bookshelf
    :moss_stone
    :obsidian
    :torch
    :fire
    :stairs_wood
    :chest
    :diamond_ore
    :diamond_block
    :diamond
    :crafting_table
    :farmland
    :furnace_inactive
    :furnace_active
    :door_wood
    :ladder
    :stairs_cobblestone
    :door_iron
    :redstone_ore
    :snow
    :ice
    :snow_block
    :cactus
    :clay
    :sugar_cane
    :fence
    :glowstone_block
    :bedrock_invisible
    :stone_brick
    :glass_pane
    :melon
    :fence_gate
    :glowing_obsidian
    :nether_reactor_core

12 Conclusions

Conclusions

This concludes the Sonic Pi introductory tutorial. Hopefully you've learned something along the way. Don't worry if you feel you didn't understand everything - just play and have fun and you'll pick things up in your own time. Feel free to dive back in when you have a question that might be covered in one of the sections.

If you have any questions that haven't been covered in the tutorial, then please jump onto the Sonic Pi forums and ask your question there. You'll find someone friendly and willing to lend a hand.

Finally, I also invite you to take a deeper look at the rest of the documentation in this help system. There are a number of features that haven't been covered in this tutorial that are waiting for your discovery.

So play, have fun, share your code, perform for your friends, show your screens and remember:

There are no mistakes, only opportunities.

Sam Aaron