This set of instructions will aid in writing two-voice polyphonic music from scratch using a simplified and modernized version of Fux's classic early-18th-century rules for species counterpoint. The only requirements are that the reader be competent enough with sheet music to read it and write it (even if slowly), and that the reader know basic musical terminology such as the names for intervals (major third, perfect fifth, etc.).
Writing species counterpoint serves as a technical exercise that helps to understand (or at least contextualize) most, if not all, Western polyphonic music during the "common practice period" and onwards. Additionally, it can serve as a simple compositional device that helps in writing polyphonic music as well.
To follow these instructions, all you will need is a way to notate music (pen and paper, or software such as MuseScore) and, ideally, a way to play it. This could be an instrument (e.g. a piano), or in the case that you're using software like MuseScore, the built-in playback mechanism may suffice.
The cantus firmus is simply a melodic line that will stay unchanging throughout the process of writing counterpoint. Here it will serve as essentially the bass line (the lower of the two lines in our two-voice polyphony). This melody will be restricted to merely a series of whole notes. Additionally, the cantus firmus must abide by what we will call the "melodic rules", which simply govern how melodies may be written, regardless of their interaction with other melodies.
Keep in mind here that "steps" are intervals of a minor or major second. "Skips" (also called "leaps") are intervals larger than a major second. Also keep in mind that the "consonant" intervals are the thirds, sixths, perfect fifths, and perfect octaves. The rest are dissonant (although the perfect fourth can in some contexts be considered consonant, this is a more subtle point).
- Intervals within a melody should often be quite small (i.e. steps), as this makes them melodically stonger, as well as easier to harmonize with later on.
- Melodic intervals should be restricted to the following intervals:
- Minor and major seconds
- Minor and major thirds
- Perfect fourths, fifths, and octaves
- Ascending minor sixths
- You shouldn't have more than one skip in a row in the same direction. If you do this anyways, at least make sure that the interval that spans the two skips is a consonant one, like a perfect fifth (and unlike a tritone or any kind of seventh).
- When writing a skip in one direction, you usually want to immediately follow up with motion in the other direction.
- The last interval in a melody (the one leading into the final note/cadence) should (usually) be a step, not a skip. This is less important for bass melodies.
Now is also a good time to choose a key/mode to write the music in. Since we are not in the common practice period anymore, it is also perfectly expected that you may not consciously choose a mode at all (although one will likely emerge if you aren't careful). For simplicity, in the example process shown here we choose the key/mode of C major/C ionian.
Below is an example cantus firmus:
Now we will be adding the second voice into the mix. We will first use "first species" style, in which we put whole notes against the whole notes of the cantus firmus, creating two voices that always move simultaneously. However, there are a few restrictions on how we do this.
First, we must follow the "melodic rules" outlined above when writing any part, including this new higher voice.
Second, we discriminate between four kinds of motion between the voices:
- Contrary means that the voices move in opposite directions (one upwards, one downwards, or vice versa). Contrary motion is the most desirable and should dominate the movement between your voices.
- Oblique means that one voice stays on the same note while the other moves. Oblique motion is always considered OK.
- Similar means that both voices move in the same direction. Similar motion is permissible only when the similar motion leads to an imperfect interval ("perfect" intervals being the perfect fouth, perfect fifth, and perfect octave).
- Parallel is a special kind of similar motion in which both voices move in the same direction by the same melodic interval type (e.g. a second), and is only permissible if the interval between the two melodies is a third or a sixth.
Third, you will want to have a "climax" for this melody. This is essentially a single note that is the high point of the whole melodic line, which must occur on a strong beat (usually the first or third beat of a measure) and tends to occur somewhere in the middle of the melody.
Fourth, start and end the piece with a perfect octave, perfect fifth, or perfect unison between the two voices.
Fifth, avoid moving in parallel thirds or sixths for too long, and avoid similar motion with melodic intervals of a skip.
Lastly, because this is the "first species", the top melody must be (like the cantus firmus) composed of only whole notes, starting on the first beat of the first measure.
Below is an example first species counterpoint using the original example cantus firmus:
This step will be similar to step 2 (the first species), except that instead of having a 1:1 correspondence between the notes in the two voices, there will be two notes on top for every note in the cantus firmus. For this purpose, the new harmonizing melody will be written in half notes instead of whole notes.
It is permissible, in the second species, to start the top melody with a half-note rest, allowing the cantus firmus to start first and having the other melody come in on the third beat of the first measure instead of the first.
There are also two additional considerations, in addition to all the considerations used in the first species:
First, the accented beat (the first beat of each measure) must be a consonant interval between the two voices, be it perfect or imperfect. The unaccented beat (the third beat of each measure) may be a dissonant interval, but only as a "passing" tone, meaning that it is both "approached" and "left" by step in the same direction.
Second, be careful not to accidentally introduce implicit parallel fifths or octaves. That means that if you have a perfect interval at the accented beat of one measure and the same perfect interval at the accented beat of the next measure, you are almost certainly doing something wrong, even if the voices on the unaccented beat(s) seem to justify it.
Below is an example second species counterpoint using the original example cantus firmus:
This step is quite similar to step 3 (the second species), except that we use quarter notes instead of half notes. Now the top melody can start with one or two quarter-note rests before entering.
The same rules for consonant and dissonant vertical intervals apply, except that now every measure has three notes that are not on an accented beat instead of just one as there was in the second species.
Additionally, we allow a new construct called "nota cambiata", which allows us to (sort of) break the rule that dissonant vertical intervals must be approached and left by step in the same direction. A dissonant interval can be approached by a step and left by a skip in the same direction, as long as you hit the "skipped note" by going up a step immediately afterwards.
Below is an example third species counterpoint using the original example cantus firmus:
In fourth species counterpoint, we use syncopation to separate the whole-note-only cantus firmus from another whole-note-only top melody. Unlike the first species, in which the top melody has only whole notes and it starts on the first beat of the first measure, the top melody in fourth species essentially starts two beats in advance of the first measure.
In this form of counterpoint, we allow dissonances on the first beat (the accented beat) of each measure due to suspension of the note from the last measure. However, each time the added voice initially hits a new note (against an already-ringing cantus firmus note), it must form a consonance. As such, the considerations are still similar to those in the second and third species.
Additionally, the penultimate measure may consist of a suspension from the last measure followed by a half note (as you would expect), or may just consist of two half notes, at the composer's discretion.
Below is an example fourth species counterpoint using the original example cantus firmus:
This "final" species is simply a species of counterpoint in which all previous species (first, second, third, and fourth) can be freely mashed together, creating a combination known as "florid" counterpoint.
Below is an example fifth species counterpoint using the original example cantus firmus, in which the second, fourth, and last bars are first-species, the third bar is second-species, the first and fifth bars are third-species, the seventh bar is fourth-species, and the sixth bar is a mix of third- and fourth-species:
Congratulations! You have now walked through all of the species of counterpoint commonly understood to be part of the technical exercise that is "species counterpoint". Understanding the arbitrary rules of these exercises intuitively puts you a long way towards intuitively analyzing and writing your own polyphony in a Western style.