midi_generator.py

"""MIDI generation module.

Creates a MIDI file from a prediction array output by interpreting and converting the data back into musical
representation by 'music21'.
"""

# Import libraries.
from music21 import instrument, note, chord, stream
import time


def create_midi(prediction_output, network_type):
    """ convert the output from the prediction to notes and create a midi file
        from the notes """

    print('Generating MIDI file...')

    offset = 0
    output_notes = []

    # Create note and chord objects based on the values generated by the model.
    for element in prediction_output:
        if ('.' in element) or element.isdigit():
            # Element is a chord.
            notes_in_chord = element.split('.')
            notes = []
            for current_note in notes_in_chord:
                new_note = note.Note(int(current_note))
                new_note.storedInstrument = instrument.Piano()
                notes.append(new_note)
            new_chord = chord.Chord(notes)
            new_chord.offset = offset
            output_notes.append(new_chord)
        else:
            # Element is a note.
            new_note = note.Note(element)
            new_note.offset = offset
            new_note.storedInstrument = instrument.Piano()
            output_notes.append(new_note)

        # Increase offset each iteration to prevent notes stacking.
        offset += 1

    midi_stream = stream.Stream(output_notes)

    file_name = 'output_' + network_type + '_' + time.strftime("%Y%m%d-%H%M%S") + '.mid'

    midi_stream.write('midi', fp=file_name)

    print('MIDI file generated.')

    midi_stream.show()