Plays from sol to sol.

Gamma.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

# Primitive NoteFactory.
# http://en.wikipedia.org/wiki/Piano_key_frequencies

T = 44000

class NoteFactory
  attr_accessor :notes, :notes_in_octave
  def initialize
    @notes = {
      sol: 47,
      la: 49,
      si: 51,
      do: 52,
      re: 54,
      mi: 56,
      fa: 58 # actually fa with bemol ^_^, else it wouldn't sound right.
    }
    @notes_in_octave = 12
  end

  def sin(n)
    Math.sin(n * 3.14/180)
  end
  def note(n)
    if not n
      p 'something\'s wrong'
      exit
    end
    freq  = 440 * 2 ** ((n - 49.0) / 12)
    $stderr.write("playing n = #{n}; freq = #{freq}\n")
    i     = 0
    q     = 360 * freq / T
    while i < T * 0.74 do
      tick = (sin(i * q) * 127) + 128
      $>.write(tick.to_i.chr)
      i = i + 1
    end
  end

end

fac = NoteFactory.new

arg, octave = ARGV.flatten.join(" ").scan(/[^ ]+/)
if octave
  octave = octave.to_i * fac.notes_in_octave
else
  octave = 0
end

fac.note(fac.notes[arg.to_sym] + octave)

__END__
#!/bin/zsh

play() { ./dsp.rb "$@" | aplay --rate=44000 2> /dev/null; }
for note in sol la si do re mi fa "sol 1"; do play $note; done