Module: MidiCreate

Includes:
MIDI
Defined in:
lib/midi_create/create.rb,
lib/midi_create/version.rb

Constant Summary collapse

VERSION = 
'0.1.0'.freeze

Class Method Summary collapse

Class Method Details

.create ⇒ Object 



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# File 'lib/midi_create/create.rb', line 22

def self.create
  seq = MIDI::Sequence.new # Create a new empty MIDI sequence.

  # Create a first track for the MIDI sequence. This holds tempo events and other data.
  track = Track.new(seq)
  seq.tracks << track
  track.events << Tempo.new(Tempo.bpm_to_mpq(@options[:bpm]))
  track.events << MetaEvent.new(META_SEQ_NAME, @options[:title]) if @options[:title]

  # Create a track to hold the notes and add it to the MIDI sequence.
  track = Track.new(seq)
  seq.tracks << track

  # Add note events to the track, corresponding to the C major scale, from C3 to C4, inclusive.
  # Arguments for note on and note off constructors are channel, note, velocity, and delta_time.
  # Channel numbers start at zero.
  # The Sequence#note_to_delta method returns the delta time length of a single quarter note.
  track.events << ProgramChange.new(0, 1, 0)
  quarter_note_length = seq.note_to_delta('quarter')

  # There is probably a more elegant way of specifying middle C,
  # which shows as C3 in Pro Tools and Ableton Live.
  # See https://studiocode.dev/resources/midi-middle-c/
  # See https://stackoverflow.com/a/69182634/553865
  c3 = 60

  [0, 2, 4, 5, 7, 9, 11, 12].each do |offset|
    track.events << NoteOn.new(0, c3 + offset, 127, 0)
    track.events << NoteOff.new(0, c3 + offset, 127, quarter_note_length)
  end

  # Write the sequence to a MIDI file.
  File.open(@midi_out, 'wb') { |file| seq.write(file) }
end

.main ⇒ Object 



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# File 'lib/midi_create/create.rb', line 6

def self.main
  @options = parse_options
  help 'The name of the output MIDI file must be provided.' if ARGV.empty?
  help "Too many parameters were specified.\n#{ARGV}" if ARGV.length > 1

  @midi_out = ARGV[0]
  if File.exist?(@midi_out)
    if @options[:overwrite]
      File.delete(@midi_out)
    else
      help "Error: File '#{@midi_out}' already exists and -f was not specified."
    end
  end
  create
end