Shepard tones example for Sonic Pi

shepard.rb

# Want to make it better?
# 1. the volume scale should center about a
#    frequency, not an octave
# 2. Check why using saw instead of sine doesn't work somehow.
# 3. The scaling with v and s shall make the overall volume
#    sounds right AND smooth the ends.
#    This should be seperated.
# 4. The smooting may be easier using subtractive synthesis
# 5. Can I create a complete synthesizer this way? What is missing?

define :shepard do |n|
  i = (note_info n)
  mn = i.midi_note
  mnr = mn % 12
  for x in [0,1,2,3,4,5,6,7,8,9,10,11]
    z = note(mnr + 12 * x)
    s = 40.0
    v = 0
    if x <= 5
      v = (x+1) / s
    else
      v = (11.5 - x)/s
    end
    synth :sine, note: z, amp: v
  end
end

n = (ring :a, :as, :b, :c, :cs, :d, :ds, :e, :f, :fs, :g, :gs).reverse
loop do
    tick
    shepard n.look
    sleep 0.4
end

Great! Thanks for this example.

Regarding no. 5, might I have written something like a complete synth here?
https://github.com/benjaminwand/Sonic-Pi-Shepard-tones-function