A Study in "A Study in Keith"

keithy-piano.rb

# Welcome to Sonic Pi v3.1
use_bpm 70
T = 4.0

# State machine utility functions
define :markov do |a, h| h[a].sample; end # Chooses the next state at  random from hash
define :g do |k| get[k]; end # simplified root note in scale getter
define :s do |k, n| set k, n; end # simplified root note setter
define :mnote do |key,chain| s key, (markov (g key), chain); g key; end
set :k, 1 # Init state


# Plays a note - this is a function in order to seamlessly use MIDI instead
define :pplay do |n, d = 0.1|
  use_synth :fm # Using FM for portability
  play n, release: d, sustain: d # This can also be MIDI
end

# Scale
sc_root = :D2
sc_type = :major
sc = scale(sc_root, sc_type)

# Chords in scale
chords = (1..7).map {|n| chord_degree n, sc_root, sc_type }.ring

# Markov chain
K = {
  1 => [7],
  7 => [1, 5],
  5 => [1, 6],
  6 => [2],
  2 => [5]
}

define :pchord do |chr, d = T|
  with_fx :level, amp: 0.5 do
    pplay chr[0], d
    pplay chr[1] + 12, d
    pplay chr[2] + 12, d
  end
end

# Main loop
live_loop :ppiano do
  chr = chords[mnote :k, K]  # get next note state from markov chain
  pchord chr # Chord (left hand)
  12.times do
    pplay chr[rrand(-2,2).to_i] + 24 # Melody (right hand)
    sleep T/16
  end
  
  chr2 = chords[mnote :k, K] # get next note state from markov chain
  pchord chr2, T/4 # Chord (left hand)
  4.times do
    pplay chr[rrand(-2,2).to_i] + 24 # Melody (right hand)
    sleep T/16
  end
end

live_loop :kick do
  p = (bools 1,0,0,1, 0,0,1,0, 0,0,0,0, 1,0,0,0)
  16.times do
    sample :bd_fat, amp: 2.5 if p.tick
    sleep T/16
  end
end

live_loop :snare do
  p = (bools 0,0,0,0, 1,0,0,0, 0,0,0,0, 1,0,0,0)
  16.times do
    sample :sn_dolf, amp: 1.0 if p.tick
    sleep T/16
  end
end