let-it-be.md

Let it be

- The Beatles

on Sonic Pi

A self-contained version of what I have in my sonic-pi-experiments repo. It uses my guitar helper, so here I've pasted it into the buffer so anyone can run it.

Here's a recording of it on Soundcloud.

let-it-be.rb

# Let it be - The Beatles (guitar)
# Uses the guitar helper

define :guitar do |tonic, name=nil, tuning=:guitar, debug=false|
  tunings = {
    :ukulele => [:g, :c, :e, :a],
    :guitar => [:e2, :a2, :d3, :g3, :b3, :e4]
  }
  tuning = tunings[tuning] || tuning
  
  # Next note higher or equal to base note n, that is in the chord c
  define :next_note do |n, c|
    # Make sure n is a number
    n = note(n)
    # Get distances to each note in chord, add smallest to base note
    n + (c.map {|x| (note(x) - n) % 12}).min
  end
  
  if tonic.respond_to?(:each) and name==nil then
    chrd = tonic
  else
    chrd = (chord tonic, name || :M)
  end
  
  # For each string, get the next higher note that is in the chord
  c = tuning.map {|n| next_note(n, chrd)}
  
  # We want the lowest note to be the root of the chord
  root = note(chrd[0])
  first_root = c.take_while {|n| (n - root) % 12 != 0}.count
  
  # Drop up to half the lowest strings to make that the case if possible
  if first_root > 0 and first_root < tuning.count / 2
    c = (ring :r) * first_root + c.drop(first_root)
  end
  
  # Display chord fingering
  if debug
    puts c.zip(tuning).map {|n, s| if n == :r then 'x' else (n - note(s)) end}.to_a.join, c
  end
  c
end

# Strum a chord with a certain delay between strings
define :guitar_strum do |chrd, dt|
  in_thread do
    play_pattern_timed chrd.to_a.drop_while{|n| [nil,:r].include? n}, dt
  end
end

define :strum do |chrd, pattern=nil, t=0.25, dt=0.025|
  if pattern == nil then
    guitar_strum(chrd, dt)
  else
    pattern.split(//).each do |shape|
      case shape
      when 'D'
        guitar_strum chrd, dt
      when 'd'
        with_fx :level, amp: 0.7 do
          guitar_strum chrd, dt
        end
      when 'U'
        with_fx :level, amp: 0.8 do
          guitar_strum chrd.reverse, dt*0.9
        end
      when 'u'
        with_fx :level, amp: 0.6 do
          guitar_strum chrd.reverse, dt*0.9
        end
      else
        # nothing
      end
      sleep t
    end
  end
end

use_bpm 72
use_synth :pluck

with_fx :reverb, room: 1 do
  with_fx :lpf, cutoff: 95 do
    2.times do
      strum guitar(:c), 'D.du', 0.5
      strum guitar(:g), 'D.du', 0.5
      strum guitar(:a, :m), 'D.', 0.5
      strum guitar(:a, :m7), 'du', 0.5
      strum guitar(:f), 'D.du', 0.5
      strum guitar(:c), 'D.du', 0.5
      strum guitar(:g), 'D.du', 0.5
      strum guitar(:f), 'D.', 0.5
      strum [:e3, :g3], 'd', 0.5
      strum [:d3, :g3], 'd', 0.5
      strum guitar(:c), 'D...', 0.5
    end
  end
end