Prototype drop-ii harmoniser in Sonic Pi

drop_2.rb

c_bebop = [60,62,64,65,67,68,69,71]
current_scale = (c_bebop.map {|x| x - 12 } + \
                 c_bebop + \
                 c_bebop.map {|x| x + 12 } + \
                 c_bebop.map {|x| x + 24 }).flatten

def chord_tones(n, scale)
  return n if n.nil?

  idx = scale.to_a.index(note(n).to_i)
  if idx.even?
    scale.to_a.select.with_index {|x, sidx| sidx >= idx && sidx.even? }.take(4)
  else
    scale.to_a.select.with_index {|x, sidx| sidx >= idx && sidx.odd? }.take(4)
  end
end

def close_harmony(n, scale)
  return n if n.nil?

  chord_tones(n, scale)
end

def drop_two(n, scale)
  return n if n.nil?
  
  chrd = chord_tones(n, scale)
  [chrd[2] - 12, chrd[0], chrd[1], chrd[3]]
end

def drop_three(n, scale)
  return n if n.nil?

  chrd = chord_tones(n, scale)
  [chrd[1] - 12, chrd[0], chrd[2], chrd[3]]
end

in_the_mood = [:c, :e, :g, :c5, nil, :c5, nil, :c5, 
               nil, :c5, nil, :c5, :b, :c5, :g, :e]

use_bpm 130
use_synth_defaults release: 0.4
use_synth :tri
play_pattern_timed in_the_mood.map {|x| drop_two(x, current_scale) }, [0.53, 0.47]

# Some experiments in making triadic harmony 
#
#def interval(n, interval, scale)
#  idx = scale.to_a.index(note(n).to_i)
#  scale.to_a.ring[idx + (interval - 1)]
#end
#
#def harm(n, scale)
#  chrd = []
#  chrd << note(n)
#  chrd << interval(chrd.last, 2, scale)
#  chrd << interval(chrd.last, 3, scale)
#  chrd << interval(chrd.last, 4, scale)
#  chrd
#end