Exemple #1
0
    def testExtractMelodiesMelodyTooLongWithPad(self):
        music_testing_lib.add_track_to_sequence(self.note_sequence, 0,
                                                [(12, 127, 2, 4),
                                                 (14, 50, 6, 15)])
        music_testing_lib.add_track_to_sequence(self.note_sequence, 1,
                                                [(12, 127, 2, 4),
                                                 (14, 50, 6, 18)])

        quantized_sequence = sequences_lib.quantize_note_sequence(
            self.note_sequence, steps_per_quarter=1)

        expected = [[
            NO_EVENT, NO_EVENT, 12, NO_EVENT, NOTE_OFF, NO_EVENT, 14, NO_EVENT,
            NO_EVENT, NO_EVENT, NO_EVENT, NO_EVENT
        ]]
        melodies, _ = melody_pipelines.extract_melodies(
            quantized_sequence,
            min_bars=1,
            max_steps_truncate=14,
            max_steps_discard=18,
            gap_bars=1,
            min_unique_pitches=2,
            ignore_polyphonic_notes=True,
            pad_end=True)
        melodies = [list(melody) for melody in melodies]
        self.assertEqual(expected, melodies)
Exemple #2
0
    def testExtractMelodiesTooFewPitches(self):
        # Test that extract_melodies discards melodies with too few pitches where
        # pitches are equivalent by octave.
        music_testing_lib.add_track_to_sequence(self.note_sequence, 0,
                                                [(12, 100, 0, 1),
                                                 (13, 100, 1, 2),
                                                 (18, 100, 2, 3),
                                                 (24, 100, 3, 4),
                                                 (25, 100, 4, 5)])
        music_testing_lib.add_track_to_sequence(self.note_sequence, 1,
                                                [(12, 100, 0, 1),
                                                 (13, 100, 1, 2),
                                                 (18, 100, 2, 3),
                                                 (25, 100, 3, 4),
                                                 (26, 100, 4, 5)])

        quantized_sequence = sequences_lib.quantize_note_sequence(
            self.note_sequence, steps_per_quarter=1)

        expected = [[12, 13, 18, 25, 26]]
        melodies, _ = melody_pipelines.extract_melodies(
            quantized_sequence,
            min_bars=1,
            gap_bars=1,
            min_unique_pitches=4,
            ignore_polyphonic_notes=True)
        melodies = [list(melody) for melody in melodies]
        self.assertEqual(expected, melodies)
Exemple #3
0
    def testExtractMultipleMelodiesFromSameTrack(self):
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                0, [(12, 100, 2, 4),
                                                    (11, 1, 6, 11)])
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                1, [(12, 127, 2, 4),
                                                    (14, 50, 6, 8),
                                                    (50, 100, 33, 37),
                                                    (52, 100, 34, 37)])

        quantized_sequence = sequences_lib.quantize_note_sequence(
            self.note_sequence, steps_per_quarter=1)

        expected = [[
            NO_EVENT, NO_EVENT, 12, NO_EVENT, NOTE_OFF, NO_EVENT, 11, NO_EVENT,
            NO_EVENT, NO_EVENT, NO_EVENT
        ], [
            NO_EVENT, NO_EVENT, 12, NO_EVENT, NOTE_OFF, NO_EVENT, 14, NO_EVENT
        ], [NO_EVENT, 50, 52, NO_EVENT, NO_EVENT]]
        melodies, _ = melody_pipelines.extract_melodies(
            quantized_sequence,
            min_bars=1,
            gap_bars=2,
            min_unique_pitches=2,
            ignore_polyphonic_notes=True)
        melodies = sorted([list(melody) for melody in melodies])
        self.assertEqual(expected, melodies)
Exemple #4
0
    def testExtractMelodiesMelodyTooShort(self):
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                0, [(12, 127, 2, 4),
                                                    (14, 50, 6, 7)])
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                1, [(12, 127, 2, 4),
                                                    (14, 50, 6, 8)])
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                2, [(12, 127, 2, 4),
                                                    (14, 50, 6, 9)])

        quantized_sequence = sequences_lib.quantize_note_sequence(
            self.note_sequence, steps_per_quarter=1)

        expected = [[
            NO_EVENT, NO_EVENT, 12, NO_EVENT, NOTE_OFF, NO_EVENT, 14, NO_EVENT
        ],
                    [
                        NO_EVENT, NO_EVENT, 12, NO_EVENT, NOTE_OFF, NO_EVENT,
                        14, NO_EVENT, NO_EVENT
                    ]]
        melodies, _ = melody_pipelines.extract_melodies(
            quantized_sequence,
            min_bars=2,
            gap_bars=1,
            min_unique_pitches=2,
            ignore_polyphonic_notes=True)
        melodies = [list(melody) for melody in melodies]
        self.assertEqual(expected, melodies)
    def testExtractChordsForMelodiesCoincidentChords(self):
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                0, [(12, 100, 2, 4),
                                                    (11, 1, 6, 11)])
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                1, [(12, 127, 2, 4),
                                                    (14, 50, 6, 8),
                                                    (50, 100, 33, 37),
                                                    (52, 100, 34, 37)])
        music_testing_lib.add_chords_to_sequence(self.note_sequence,
                                                 [('C', 2), ('G7', 6),
                                                  ('E13', 8), ('Cmaj7', 8)])
        quantized_sequence = sequences_lib.quantize_note_sequence(
            self.note_sequence, self.steps_per_quarter)

        melodies, _ = melody_pipelines.extract_melodies(
            quantized_sequence,
            min_bars=1,
            gap_bars=2,
            min_unique_pitches=2,
            ignore_polyphonic_notes=True)
        chord_progressions, stats = chord_pipelines.extract_chords_for_melodies(
            quantized_sequence, melodies)
        expected = [[NO_CHORD, NO_CHORD, 'C', 'C', 'C', 'C', 'G7', 'G7'],
                    ['Cmaj7', 'Cmaj7', 'Cmaj7', 'Cmaj7', 'Cmaj7']]
        stats_dict = dict((stat.name, stat) for stat in stats)
        self.assertIsNone(chord_progressions[0])
        self.assertEqual(expected,
                         [list(chords) for chords in chord_progressions[1:]])
        self.assertEqual(stats_dict['coincident_chords'].count, 1)
Exemple #6
0
 def testExtractLeadSheetFragmentsCoincidentChords(self):
     music_testing_lib.add_track_to_sequence(self.note_sequence,
                                             0, [(12, 100, 2, 4),
                                                 (11, 1, 6, 11)])
     music_testing_lib.add_track_to_sequence(self.note_sequence,
                                             1, [(12, 127, 2, 4),
                                                 (14, 50, 6, 8),
                                                 (50, 100, 33, 37),
                                                 (52, 100, 34, 37)])
     music_testing_lib.add_chords_to_sequence(self.note_sequence,
                                              [('C', 2), ('G7', 6),
                                               ('Cmaj7', 33), ('F', 33)])
     quantized_sequence = sequences_lib.quantize_note_sequence(
         self.note_sequence, steps_per_quarter=1)
     lead_sheets, _ = lead_sheet_pipelines.extract_lead_sheet_fragments(
         quantized_sequence,
         min_bars=1,
         gap_bars=2,
         min_unique_pitches=2,
         ignore_polyphonic_notes=True,
         require_chords=True)
     melodies, _ = melody_pipelines.extract_melodies(
         quantized_sequence,
         min_bars=1,
         gap_bars=2,
         min_unique_pitches=2,
         ignore_polyphonic_notes=True)
     chord_progressions, _ = chord_pipelines.extract_chords_for_melodies(
         quantized_sequence, melodies)
     # Last lead sheet should be rejected for coincident chords.
     self.assertEqual(list(melodies[:2]),
                      list(lead_sheet.melody for lead_sheet in lead_sheets))
     self.assertEqual(list(chord_progressions[:2]),
                      list(lead_sheet.chords for lead_sheet in lead_sheets))
    def testExtractChordsForMelodies(self):
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                0, [(12, 100, 2, 4),
                                                    (11, 1, 6, 11)])
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                1, [(12, 127, 2, 4),
                                                    (14, 50, 6, 8),
                                                    (50, 100, 33, 37),
                                                    (52, 100, 34, 37)])
        music_testing_lib.add_chords_to_sequence(self.note_sequence,
                                                 [('C', 2), ('G7', 6),
                                                  ('Cmaj7', 33)])
        quantized_sequence = sequences_lib.quantize_note_sequence(
            self.note_sequence, self.steps_per_quarter)

        melodies, _ = melody_pipelines.extract_melodies(
            quantized_sequence,
            min_bars=1,
            gap_bars=2,
            min_unique_pitches=2,
            ignore_polyphonic_notes=True)
        chord_progressions, _ = chord_pipelines.extract_chords_for_melodies(
            quantized_sequence, melodies)
        expected = [[
            NO_CHORD, NO_CHORD, 'C', 'C', 'C', 'C', 'G7', 'G7', 'G7', 'G7',
            'G7'
        ], [NO_CHORD, NO_CHORD, 'C', 'C', 'C', 'C', 'G7', 'G7'],
                    ['G7', 'Cmaj7', 'Cmaj7', 'Cmaj7', 'Cmaj7']]
        self.assertEqual(expected,
                         [list(chords) for chords in chord_progressions])
Exemple #8
0
 def testExtractLeadSheetFragments(self):
     music_testing_lib.add_track_to_sequence(self.note_sequence, 0,
                                             [(12, 100, .5, 1),
                                              (11, 1, 1.5, 2.75)])
     music_testing_lib.add_track_to_sequence(self.note_sequence, 1,
                                             [(12, 127, .5, 1),
                                              (14, 50, 1.5, 2),
                                              (50, 100, 8.25, 9.25),
                                              (52, 100, 8.5, 9.25)])
     music_testing_lib.add_chords_to_sequence(self.note_sequence,
                                              [('C', .5), ('G7', 1.5),
                                               ('Cmaj7', 8.25)])
     quantized_sequence = sequences_lib.quantize_note_sequence(
         self.note_sequence, self.steps_per_quarter)
     lead_sheets, _ = lead_sheet_pipelines.extract_lead_sheet_fragments(
         quantized_sequence,
         min_bars=1,
         gap_bars=2,
         min_unique_pitches=2,
         ignore_polyphonic_notes=True,
         require_chords=True)
     melodies, _ = melody_pipelines.extract_melodies(
         quantized_sequence,
         min_bars=1,
         gap_bars=2,
         min_unique_pitches=2,
         ignore_polyphonic_notes=True)
     chord_progressions, _ = chord_pipelines.extract_chords_for_melodies(
         quantized_sequence, melodies)
     self.assertEqual(list(melodies),
                      list(lead_sheet.melody for lead_sheet in lead_sheets))
     self.assertEqual(list(chord_progressions),
                      list(lead_sheet.chords for lead_sheet in lead_sheets))
Exemple #9
0
  def testExtractMelodiesStatistics(self):
    music_testing_lib.add_track_to_sequence(
        self.note_sequence, 0,
        [(12, 100, 2, 4), (11, 1, 6, 7), (10, 100, 8, 10), (9, 100, 11, 14),
         (8, 100, 16, 40), (7, 100, 41, 42)])
    music_testing_lib.add_track_to_sequence(
        self.note_sequence, 1,
        [(12, 127, 2, 4), (14, 50, 2, 8)])
    music_testing_lib.add_track_to_sequence(
        self.note_sequence, 2,
        [(12, 127, 0, 1)])
    music_testing_lib.add_track_to_sequence(
        self.note_sequence, 3,
        [(12, 127, 2, 4), (12, 50, 6, 8)])

    quantized_sequence = sequences_lib.quantize_note_sequence(
        self.note_sequence, steps_per_quarter=1)

    _, stats = melody_pipelines.extract_melodies(
        quantized_sequence, min_bars=1, gap_bars=1, min_unique_pitches=2,
        ignore_polyphonic_notes=False)

    stats_dict = dict((stat.name, stat) for stat in stats)
    self.assertEqual(stats_dict['polyphonic_tracks_discarded'].count, 1)
    self.assertEqual(stats_dict['melodies_discarded_too_short'].count, 1)
    self.assertEqual(stats_dict['melodies_discarded_too_few_pitches'].count, 1)
    self.assertEqual(
        stats_dict['melody_lengths_in_bars'].counters,
        {float('-inf'): 0, 0: 0, 1: 0, 2: 0, 10: 1, 20: 0, 30: 0, 40: 0, 50: 0,
         100: 0, 200: 0, 500: 0})
Exemple #10
0
    def testExtractMelodiesSimple(self):
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                0, [(12, 100, 2, 4),
                                                    (11, 1, 6, 7)])
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                1, [(12, 127, 2, 4),
                                                    (14, 50, 6, 9)])
        music_testing_lib.add_track_to_sequence(self.note_sequence,
                                                9, [(13, 100, 2, 4),
                                                    (15, 25, 6, 8)],
                                                is_drum=True)

        quantized_sequence = sequences_lib.quantize_note_sequence(
            self.note_sequence, steps_per_quarter=1)

        expected = [[NO_EVENT, NO_EVENT, 12, NO_EVENT, NOTE_OFF, NO_EVENT, 11],
                    [
                        NO_EVENT, NO_EVENT, 12, NO_EVENT, NOTE_OFF, NO_EVENT,
                        14, NO_EVENT, NO_EVENT
                    ]]
        melodies, _ = melody_pipelines.extract_melodies(
            quantized_sequence,
            min_bars=1,
            gap_bars=1,
            min_unique_pitches=2,
            ignore_polyphonic_notes=True)

        self.assertEqual(2, len(melodies))
        self.assertIsInstance(melodies[0], melodies_lib.Melody)
        self.assertIsInstance(melodies[1], melodies_lib.Melody)

        melodies = sorted([list(melody) for melody in melodies])
        self.assertEqual(expected, melodies)
Exemple #11
0
    def emissionModelTrainer(self):
        ALL_CHORD_LIST = ['N.C', 'C', 'Cm', 'C#', 'C#m', 'D', 'Dm', 'Eb', 'Ebm', 'E', 'Em', 'F', 'Fm', 'F#', 'F#m', 'G',
                          'Gm', 'G#', 'G#m', 'A', 'Am', 'A#', 'A#m', 'B', 'Bm']
        Same_Chord = {'Db': 'C#', 'Dbm': 'C#m', 'D#': 'Eb', 'D#m': 'Ebm', 'Gb': 'F#', 'Gbm': 'F#m', 'Ab': 'G#',
                      'Abm': 'G#m', 'Bb': 'A#', 'Bbm': 'A#m'}
        ALL_NOTE_LIST = ['C', 'C#', 'D', 'Eb', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B']


        path = "D:\FAI\Wikifonia"
        for file in glob.glob(path):
            mxlObject = musicxml_parser.MusicXMLDocument(file)
            mxlSequence = musicxml_reader.musicxml_to_sequence_proto(mxlObject)
            quantizedNoteSequence = sequences_lib.quantize_note_sequence(mxlSequence, 1)

            melodies, stats = melody_pipelines.extract_melodies(quantizedNoteSequence)

            chord_prog, stats = chord_pipelines.extract_chords_for_melodies(quantizedNoteSequence, melodies)
            if not chord_prog:
                continue
            for i in range(len(list(chord_prog[0]))):
                curChord = list(chord_prog[0])[i]
                curMel = list(melodies[0])[i]
                while (curMel > 71):
                    curMel = curMel - 12
                while (curMel < 60):
                    curMel = curMel + 12
                curChord = re.sub(r'\d+', '', curChord)
                curChord = curChord[:3]
                if curChord not in 'N.C.':
                    if len(curChord) == 3 and curChord[2] not in 'm':
                        curChord = curChord[:2]
                        if curChord[1] not in ['#', 'b']:
                            curChord = curChord[:1]

                if curChord in Same_Chord:
                    curChord = Same_Chord[curChord]

                if curChord in 'Cb':
                    curChord = 'B'

                if curChord in 'Fb':
                    curChord = 'E'

                if curChord in 'Cbm':
                    curChord = 'D'

                if curChord in 'Fbm':
                    curChord = 'Em'

                a = ALL_CHORD_LIST.index(re.sub(r'\d+', '', curChord))
                b = curMel
                self.mo_matrix[a][b - 60] = self.mo_matrix[a][b - 60] + 1

        normed_mo_matrix = normalize(self.mo_matrix, axis=1, norm='l1')
        self.mo_matrix = normed_mo_matrix
Exemple #12
0
    def extractPitch(self, song):
        seq = midi_io.midi_file_to_note_sequence(song)
        qseq = sequences_lib.quantize_note_sequence(seq, 1)
        melodies, stats = melody_pipelines.extract_melodies(qseq)
        rounded_pitches = []
        for mel in list(melodies[0]):
            while (mel > 71):
                mel = mel - 12
            while (mel < 60):
                mel = mel + 12
            rounded_pitches.append(mel)

        return rounded_pitches
Exemple #13
0
    def cleanDataset(self):

        path = "D:\FAI\Wikifonia"
        count = 0
        for file in glob.glob(path):
            try:
                mxlObject = musicxml_parser.MusicXMLDocument(file)
                mxlSequence = musicxml_reader.musicxml_to_sequence_proto(mxlObject)
                quantizedNoteSequence = sequences_lib.quantize_note_sequence(mxlSequence, 1)
                chord_prog, stats = chord_pipelines.extract_chords(quantizedNoteSequence)
                melodies, stats = melody_pipelines.extract_melodies(quantizedNoteSequence)
                ac, stats = chord_pipelines.extract_chords_for_melodies(quantizedNoteSequence, melodies)
            except:
                os.remove(file)
                print(file)
                count = count + 1
Exemple #14
0
  def load_primer(self):
    """Loads default MIDI primer file.

    Also assigns the steps per bar of this file to be the model's defaults.
    """

    if not os.path.exists(self.midi_primer):
      tf.logging.warn('ERROR! No such primer file exists! %s', self.midi_primer)
      return

    self.primer_sequence = midi_io.midi_file_to_sequence_proto(self.midi_primer)
    quantized_seq = sequences_lib.quantize_note_sequence(
        self.primer_sequence, steps_per_quarter=4)
    extracted_melodies, _ = melody_pipelines.extract_melodies(
        quantized_seq, min_bars=0, min_unique_pitches=1)
    self.primer = extracted_melodies[0]
    self.steps_per_bar = self.primer.steps_per_bar
Exemple #15
0
  def testExtractMelodiesLateStart(self):
    music_testing_lib.add_track_to_sequence(
        self.note_sequence, 0,
        [(12, 100, 102, 103), (13, 100, 104, 106)])
    music_testing_lib.add_track_to_sequence(
        self.note_sequence, 1,
        [(12, 100, 100, 101), (13, 100, 102, 105)])

    quantized_sequence = sequences_lib.quantize_note_sequence(
        self.note_sequence, steps_per_quarter=1)

    expected = [[NO_EVENT, NO_EVENT, 12, NOTE_OFF, 13, NO_EVENT],
                [12, NOTE_OFF, 13, NO_EVENT, NO_EVENT]]
    melodies, _ = melody_pipelines.extract_melodies(
        quantized_sequence, min_bars=1, gap_bars=1, min_unique_pitches=2,
        ignore_polyphonic_notes=True)
    melodies = sorted([list(melody) for melody in melodies])
    self.assertEqual(expected, melodies)
def extract_lead_sheet_fragments(quantized_sequence,
                                 search_start_step=0,
                                 min_bars=7,
                                 max_steps_truncate=None,
                                 max_steps_discard=None,
                                 gap_bars=1.0,
                                 min_unique_pitches=5,
                                 ignore_polyphonic_notes=True,
                                 pad_end=False,
                                 filter_drums=True,
                                 require_chords=False,
                                 all_transpositions=False):
    """Extracts a list of lead sheet fragments from a quantized NoteSequence.

  This function first extracts melodies using melodies_lib.extract_melodies,
  then extracts the chords underlying each melody using
  chords_lib.extract_chords_for_melodies.

  Args:
    quantized_sequence: A quantized NoteSequence object.
    search_start_step: Start searching for a melody at this time step. Assumed
        to be the first step of a bar.
    min_bars: Minimum length of melodies in number of bars. Shorter melodies are
        discarded.
    max_steps_truncate: Maximum number of steps in extracted melodies. If
        defined, longer melodies are truncated to this threshold. If pad_end is
        also True, melodies will be truncated to the end of the last bar below
        this threshold.
    max_steps_discard: Maximum number of steps in extracted melodies. If
        defined, longer melodies are discarded.
    gap_bars: A melody comes to an end when this number of bars (measures) of
        silence is encountered.
    min_unique_pitches: Minimum number of unique notes with octave equivalence.
        Melodies with too few unique notes are discarded.
    ignore_polyphonic_notes: If True, melodies will be extracted from
        `quantized_sequence` tracks that contain polyphony (notes start at the
        same time). If False, tracks with polyphony will be ignored.
    pad_end: If True, the end of the melody will be padded with NO_EVENTs so
        that it will end at a bar boundary.
    filter_drums: If True, notes for which `is_drum` is True will be ignored.
    require_chords: If True, only return lead sheets that have at least one
        chord other than NO_CHORD. If False, lead sheets with only melody will
        also be returned.
    all_transpositions: If True, also transpose each lead sheet fragment into
        all 12 keys.

  Returns:
    A python list of LeadSheet instances.

  Raises:
    NonIntegerStepsPerBarError: If `quantized_sequence`'s bar length
        (derived from its time signature) is not an integer number of time
        steps.
  """
    sequences_lib.assert_is_relative_quantized_sequence(quantized_sequence)
    stats = dict([('empty_chord_progressions',
                   statistics.Counter('empty_chord_progressions'))])
    melodies, melody_stats = melody_pipelines.extract_melodies(
        quantized_sequence,
        search_start_step=search_start_step,
        min_bars=min_bars,
        max_steps_truncate=max_steps_truncate,
        max_steps_discard=max_steps_discard,
        gap_bars=gap_bars,
        min_unique_pitches=min_unique_pitches,
        ignore_polyphonic_notes=ignore_polyphonic_notes,
        pad_end=pad_end,
        filter_drums=filter_drums)
    chord_progressions, chord_stats = chord_pipelines.extract_chords_for_melodies(
        quantized_sequence, melodies)
    lead_sheets = []
    for melody, chords in zip(melodies, chord_progressions):
        # If `chords` is None, it's because a chord progression could not be
        # extracted for this particular melody.
        if chords is not None:
            if require_chords and all(chord == chords_lib.NO_CHORD
                                      for chord in chords):
                stats['empty_chord_progressions'].increment()
            else:
                lead_sheet = LeadSheet(melody, chords)
                if all_transpositions:
                    for amount in range(-6, 6):
                        transposed_lead_sheet = copy.deepcopy(lead_sheet)
                        transposed_lead_sheet.transpose(amount)
                        lead_sheets.append(transposed_lead_sheet)
                else:
                    lead_sheets.append(lead_sheet)
    return lead_sheets, list(stats.values()) + melody_stats + chord_stats
  def _generate(self, input_sequence, generator_options):
    if len(generator_options.input_sections) > 1:
      raise sequence_generator.SequenceGeneratorError(
          'This model supports at most one input_sections message, but got %s' %
          len(generator_options.input_sections))
    if len(generator_options.generate_sections) != 1:
      raise sequence_generator.SequenceGeneratorError(
          'This model supports only 1 generate_sections message, but got %s' %
          len(generator_options.generate_sections))

    if input_sequence and input_sequence.tempos:
      qpm = input_sequence.tempos[0].qpm
    else:
      qpm = note_seq.DEFAULT_QUARTERS_PER_MINUTE
    steps_per_second = note_seq.steps_per_quarter_to_steps_per_second(
        self.steps_per_quarter, qpm)

    generate_section = generator_options.generate_sections[0]
    if generator_options.input_sections:
      input_section = generator_options.input_sections[0]
      primer_sequence = note_seq.trim_note_sequence(input_sequence,
                                                    input_section.start_time,
                                                    input_section.end_time)
      input_start_step = note_seq.quantize_to_step(
          input_section.start_time, steps_per_second, quantize_cutoff=0)
    else:
      primer_sequence = input_sequence
      input_start_step = 0

    if primer_sequence.notes:
      last_end_time = max(n.end_time for n in primer_sequence.notes)
    else:
      last_end_time = 0
    if last_end_time > generate_section.start_time:
      raise sequence_generator.SequenceGeneratorError(
          'Got GenerateSection request for section that is before the end of '
          'the NoteSequence. This model can only extend sequences. Requested '
          'start time: %s, Final note end time: %s' %
          (generate_section.start_time, last_end_time))

    # Quantize the priming sequence.
    quantized_sequence = note_seq.quantize_note_sequence(
        primer_sequence, self.steps_per_quarter)
    # Setting gap_bars to infinite ensures that the entire input will be used.
    extracted_melodies, _ = melody_pipelines.extract_melodies(
        quantized_sequence, search_start_step=input_start_step, min_bars=0,
        min_unique_pitches=1, gap_bars=float('inf'),
        ignore_polyphonic_notes=True)
    assert len(extracted_melodies) <= 1

    start_step = note_seq.quantize_to_step(
        generate_section.start_time, steps_per_second, quantize_cutoff=0)
    # Note that when quantizing end_step, we set quantize_cutoff to 1.0 so it
    # always rounds down. This avoids generating a sequence that ends at 5.0
    # seconds when the requested end time is 4.99.
    end_step = note_seq.quantize_to_step(
        generate_section.end_time, steps_per_second, quantize_cutoff=1.0)

    if extracted_melodies and extracted_melodies[0]:
      melody = extracted_melodies[0]
    else:
      # If no melody could be extracted, create an empty melody that starts 1
      # step before the request start_step. This will result in 1 step of
      # silence when the melody is extended below.
      steps_per_bar = int(
          note_seq.steps_per_bar_in_quantized_sequence(quantized_sequence))
      melody = note_seq.Melody([],
                               start_step=max(0, start_step - 1),
                               steps_per_bar=steps_per_bar,
                               steps_per_quarter=self.steps_per_quarter)

    # Ensure that the melody extends up to the step we want to start generating.
    melody.set_length(start_step - melody.start_step)

    # Extract generation arguments from generator options.
    arg_types = {
        'temperature': lambda arg: arg.float_value,
        'beam_size': lambda arg: arg.int_value,
        'branch_factor': lambda arg: arg.int_value,
        'steps_per_iteration': lambda arg: arg.int_value
    }
    args = dict((name, value_fn(generator_options.args[name]))
                for name, value_fn in arg_types.items()
                if name in generator_options.args)

    generated_melody = self._model.generate_melody(
        end_step - melody.start_step, melody, **args)
    generated_sequence = generated_melody.to_sequence(qpm=qpm)
    assert (generated_sequence.total_time - generate_section.end_time) <= 1e-5
    return generated_sequence