MML から Sequencer オブジェクト生成サンプル

mml.rb

require 'strscan'
require 'rubysketch'
using RubySketch

B = Beeps

class MMLCompiler

  def compile(str)
    scanner  = StringScanner.new str.gsub(/;.*\n/, '')
    seq      = B::Sequencer.new
    bpm      = 120
    time     = 0
    tone     = 0
    octave   = 4
    length   = 4
    velocity = 127

    scanner.skip /\s*/
    until scanner.empty?
      case
      when scanner.scan(/T\s*(\d+)/i)
        bpm      = scanner[1].to_i
      when scanner.scan(/O\s*(\d+)/i)
        octave   = scanner[1].to_i
      when scanner.scan(/L\s*(\d+)/i)
        length   = scanner[1].to_i
      when scanner.scan(/V\s*(\d+)/i)
        velocity = scanner[1].to_i
      when scanner.scan(/R\s*(\d+)?/i)
        time    += seconds scanner[1]&.to_i || length, bpm
      when scanner.scan(/@\s*(\d+)/)
        tone     = scanner[1].to_i
      when scanner.scan(/([<>])/)
        case scanner[1]
        when '<' then octave -= 1
        when '>' then octave += 1
        end
      when scanner.scan(/([CDEFGAB])\s*([#+-]+)?\s*(\d+)?\s*(\.+)?/i)&.chomp
        char, offset, len, dots = [1, 2, 3, 4].map {scanner[_1]}

        freq = frequency(char, offset, octave) or next
        sec  = seconds len&.to_i || length, bpm
        sec *= 1 + dots.size.times.map {0.5 / (_1 + 1)}.sum if dots
        osc  = B::Oscillator.new TONES[tone], freq: freq
        env  = B::Envelope.new {note_on; note_off (sec - 0.01).clamp(0.01..)}
        gain = B::Gain.new gain: velocity.clamp(0, 127) / 127.0 * 0.5
        seq.add osc >> env >> gain, time, sec
        time += sec
      else
        raise "Unknown input: #{scanner.rest[..10]}"
      end
      scanner.skip /\s*/
    end
    seq
  end

  private

  TONES     = [:sine, :triangle, :square, :sawtooth]

  DISTANCES = -> {
    notes   = 'c_d_ef_g_a_b'.each_char.with_index.reject {|c,| c == '_'}.to_a
    octaves = (0..11).to_a
    octaves.product(notes)
      .map.with_object({}) {|(octave, (note, index)), hash|
        hash[[note, octave]] = octave * 12 + index - 57
      }
  }.call

  def frequency(note, offset, octave)
    raise "Bad note: '#{note}'" unless note =~ /[cdefgab]/i

    distance  = DISTANCES[[note.downcase, octave]]
    distance += (offset || '').each_char.reduce(0) {|value, char|
      case char
      when '+', '#' then value + 1
      when '-'      then value - 1
      else               value
      end
    }
    440 * (2 ** (distance.to_f / 12))
  end

  def seconds(length, bpm)
    60.0 / bpm / length
  end

end# MMLCompiler

setup do
  ellipseMode CENTER
  background 0
  textSize 30
  text "Click!", 10, 100
end

mousePressed do
  circle mouseX, mouseY, 50
  seq1 = MMLCompiler.new.compile '@1 ffffre-rgrf1'
  seq2 = MMLCompiler.new.compile '@1 c<bb-argrb-ra1'
  B::Sound.new(seq1, 3).play
  B::Sound.new(seq2, 3).play
end