Arpeggiator in Sonic Pi

README.md

Arpeggiator in Sonic Pi

This is a work in progress

arp.rb

#ARGS
#root

#octaves - 0 == just the root, 2 equals root -> root + 24
#chord: chord type
#direction: one of :up, :down, :updown, :random, :none
#transpose: convenience for transpose
#group: 1 - group the notes after the pattern has been decided

#(alternative)
#notes: array of notes which will have octave data removed
#pattern: array of indexes into the pattern

#(? not sure)
#hold: don't remove notes

define :arpeggiator do |root, options={}|
  options[:num_octaves] ||= 1
  options[:direction] ||= :up
  options[:transpose] ||= nil
  options[:grouping] ||= 0

  options[:chord] ||= :major
  options[:scale] ||= nil
  options[:notes] ||= nil

  if options[:notes]
    # TODO: num_octaves for arbitrary notes
    note_pool = Array(options[:notes]).ring
  elsif options[:scale]
    note_pool = scale(root, options[:scale], num_octaves: options[:num_octaves])
  else
    note_pool = options[:num_octaves].times.flat_map do |n|
      chord(root, options[:chord]).map {|x| x + (n * 12) }
    end
  end

  # safety net
  note_pool = Array(root) if note_pool.empty?

  # Make array for following transformations
  note_pool = note_pool.to_a

  note_pool = case options[:direction]
  when :up
    note_pool.sort
  when :down
    note_pool.sort.reverse
  when :updown
    note_pool.sort + note_pool.sort.reverse[1..-1]
  when :downup
    note_pool.sort.reverse + note_pool.sort[1..-1]
  when :random
    note_pool.shuffle
  when :from_notes
    note_pool
  end

  note_pool = if options[:grouping] != 0
    # TODO stop this crashing if grouping > note_pool.length
    note_pool.each_cons(options[:grouping]).to_a.flatten
  else
    note_pool
  end

  (ring *note_pool)
end

use_synth :fm

live_loop :arp do
  play arpeggiator(:c4, num_octaves: 2, chord: :m7).tick, release: 0.1
  sleep 0.125

  # or  
  #play arpeggiator(:c4, num_octaves: 3, scale: :minor_pentatonic, direction: :down, grouping: 4).tick, release: 0.05
  #sleep 0.0625
end