aiexperiments-ai-duet/server/magenta/music/chords_lib.py
2016-11-17 07:33:16 +03:00

543 lines
18 KiB
Python

# Copyright 2016 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Utility functions for working with chord progressions.
Use extract_chords_for_melodies to extract chord progressions from a
QuantizedSequence object, aligned with already-extracted melodies.
Use ChordProgression.to_sequence to write a chord progression to a
NoteSequence proto, encoding the chords as text annotations.
"""
import abc
from six.moves import range # pylint: disable=redefined-builtin
from magenta.music import chord_symbols_lib
from magenta.music import constants
from magenta.music import events_lib
from magenta.pipelines import statistics
from magenta.protobuf import music_pb2
STANDARD_PPQ = constants.STANDARD_PPQ
NOTES_PER_OCTAVE = constants.NOTES_PER_OCTAVE
NO_CHORD = constants.NO_CHORD
# Shortcut to CHORD_SYMBOL annotation type.
CHORD_SYMBOL = music_pb2.NoteSequence.TextAnnotation.CHORD_SYMBOL
class CoincidentChordsException(Exception):
pass
class BadChordException(Exception):
pass
class ChordEncodingException(Exception):
pass
class ChordProgression(events_lib.SimpleEventSequence):
"""Stores a quantized stream of chord events.
ChordProgression is an intermediate representation that all chord or lead
sheet models can use. Chords are represented here by a chord symbol string;
model-specific code is responsible for converting this representation to
SequenceExample protos for TensorFlow.
ChordProgression implements an iterable object. Simply iterate to retrieve
the chord events.
ChordProgression events are chord symbol strings like "Cm7", with special
event NO_CHORD to indicate no chordal harmony. When a chord lasts for longer
than a single step, the chord symbol event is repeated multiple times. Note
that this is different from MonophonicMelody, where the special
MELODY_NO_EVENT is used for subsequent steps of sustained notes; in the case
of harmony, there's no distinction between a repeated chord and a sustained
chord.
Chords must be inserted in ascending order by start time.
Attributes:
start_step: The offset of the first step of the progression relative to the
beginning of the source sequence.
end_step: The offset to the beginning of the bar following the last step
of the progression relative to the beginning of the source sequence.
steps_per_quarter: Number of steps in in a quarter note.
steps_per_bar: Number of steps in a bar (measure) of music.
"""
def __init__(self):
"""Construct an empty ChordProgression."""
super(ChordProgression, self).__init__(pad_event=NO_CHORD)
def __deepcopy__(self, unused_memo=None):
new_copy = type(self)()
new_copy.from_event_list(list(self._events),
self.start_step,
self.steps_per_bar,
self.steps_per_quarter)
return new_copy
def __eq__(self, other):
if not isinstance(other, ChordProgression):
return False
else:
return super(ChordProgression, self).__eq__(other)
def _add_chord(self, figure, start_step, end_step):
"""Adds the given chord to the `events` list.
`start_step` is set to the given chord. Everything after `start_step` in
`events` is deleted before the chord is added. `events`'s length will be
changed so that the last event has index `end_step` - 1.
Args:
figure: Chord symbol figure. A string like "Cm9" representing the chord.
start_step: A non-negative integer step that the chord begins on.
end_step: An integer step that the chord ends on. The chord is considered
to end at the onset of the end step. `end_step` must be greater than
`start_step`.
Raises:
BadChordException: If `start_step` does not precede `end_step`.
"""
if start_step >= end_step:
raise BadChordException(
'Start step does not precede end step: start=%d, end=%d' %
(start_step, end_step))
self.set_length(end_step)
for i in range(start_step, end_step):
self._events[i] = figure
def from_quantized_sequence(self, quantized_sequence, start_step, end_step):
"""Populate self with the chords from the given QuantizedSequence object.
A chord progression is extracted from the given sequence starting at time
step `start_step` and ending at time step `end_step`.
The number of time steps per bar is computed from the time signature in
`quantized_sequence`.
Args:
quantized_sequence: A sequences_lib.QuantizedSequence instance.
start_step: Start populating chords at this time step.
end_step: Stop populating chords at this time step.
Raises:
NonIntegerStepsPerBarException: If `quantized_sequence`'s bar length
(derived from its time signature) is not an integer number of time
steps.
CoincidentChordsException: If any of the chords start on the same step.
"""
self._reset()
steps_per_bar_float = quantized_sequence.steps_per_bar()
if steps_per_bar_float % 1 != 0:
raise events_lib.NonIntegerStepsPerBarException(
'There are %f timesteps per bar. Time signature: %d/%d' %
(steps_per_bar_float, quantized_sequence.time_signature.numerator,
quantized_sequence.time_signature.denominator))
self._steps_per_bar = int(steps_per_bar_float)
self._steps_per_quarter = quantized_sequence.steps_per_quarter
# Sort track by chord times.
chords = sorted(quantized_sequence.chords, key=lambda chord: chord.step)
prev_step = None
prev_figure = NO_CHORD
for chord in chords:
if chord.step >= end_step:
# No more chords within range.
break
elif chord.step < start_step:
# Chord is before start of range.
prev_step = chord.step
prev_figure = chord.figure
continue
if chord.step == prev_step:
if chord.figure == prev_figure:
# Identical coincident chords, just skip.
continue
else:
# Two different chords start at the same time step.
self._reset()
raise CoincidentChordsException('chords %s and %s are coincident' %
(prev_figure, chord.figure))
if chord.step > start_step:
# Add the previous chord.
start_index = max(prev_step, start_step) - start_step
end_index = chord.step - start_step
self._add_chord(prev_figure, start_index, end_index)
prev_step = chord.step
prev_figure = chord.figure
if prev_step < end_step:
# Add the last chord active before end_step.
start_index = max(prev_step, start_step) - start_step
end_index = end_step - start_step
self._add_chord(prev_figure, start_index, end_index)
self._start_step = start_step
self._end_step = end_step
def to_sequence(self,
sequence_start_time=0.0,
qpm=120.0):
"""Converts the ChordProgression to NoteSequence proto.
This doesn't generate actual notes, but text annotations specifying the
chord changes when they occur.
Args:
sequence_start_time: A time in seconds (float) that the first chord in
the sequence will land on.
qpm: Quarter notes per minute (float).
Returns:
A NoteSequence proto encoding the given chords as text annotations.
"""
seconds_per_step = 60.0 / qpm / self.steps_per_quarter
sequence = music_pb2.NoteSequence()
sequence.tempos.add().qpm = qpm
sequence.ticks_per_quarter = STANDARD_PPQ
current_figure = NO_CHORD
for step, figure in enumerate(self):
if figure != current_figure:
current_figure = figure
chord = sequence.text_annotations.add()
chord.time = step * seconds_per_step + sequence_start_time
chord.text = figure
chord.annotation_type = CHORD_SYMBOL
return sequence
def transpose(self, transpose_amount, chord_symbol_functions=
chord_symbols_lib.ChordSymbolFunctions.get()):
"""Transpose chords in this ChordProgression.
Args:
transpose_amount: The number of half steps to transpose this
ChordProgression. Positive values transpose up. Negative values
transpose down.
chord_symbol_functions: ChordSymbolFunctions object with which to perform
the actual transposition of chord symbol strings.
Raises:
ChordSymbolException: If a chord (other than "no chord") fails to be
interpreted by the ChordSymbolFunctions object.
"""
for i in xrange(len(self._events)):
if self._events[i] != NO_CHORD:
self._events[i] = chord_symbol_functions.transpose_chord_symbol(
self._events[i], transpose_amount % NOTES_PER_OCTAVE)
def extract_chords_for_melodies(quantized_sequence, melodies):
"""Extracts from the QuantizedSequence a chord progression for each melody.
This function will extract the underlying chord progression (encoded as text
annotations) from `quantized_sequence` for each monophonic melody in
`melodies`. Each chord progression will be the same length as its
corresponding melody.
Args:
quantized_sequence: A sequences_lib.QuantizedSequence object.
melodies: A python list of MonophonicMelody instances.
Returns:
A python list of ChordProgression instances, the same length as `melodies`.
If a progression fails to be extracted for a melody, the corresponding
list entry will be None.
"""
chord_progressions = []
stats = dict([('coincident_chords', statistics.Counter('coincident_chords'))])
for melody in melodies:
try:
chords = ChordProgression()
chords.from_quantized_sequence(
quantized_sequence, melody.start_step, melody.end_step)
except CoincidentChordsException:
stats['coincident_chords'].increment()
chords = None
chord_progressions.append(chords)
return chord_progressions, stats.values()
class ChordRenderer(object):
"""An abstract class for rendering NoteSequence chord symbols as notes."""
__metaclass__ = abc.ABCMeta
@abc.abstractmethod
def render(self, sequence):
"""Renders the chord symbols of a NoteSequence.
This function renders chord symbol annotations in a NoteSequence as actual
notes. Notes are added to the NoteSequence object, and the chord symbols
remain also.
Args:
sequence: The NoteSequence for which to render chord symbols.
"""
pass
class BasicChordRenderer(ChordRenderer):
"""A chord renderer that holds each note for the duration of the chord."""
def __init__(self,
velocity=100,
instrument=1,
program=88,
chord_symbol_functions=
chord_symbols_lib.ChordSymbolFunctions.get()):
"""Initialize a BasicChordRenderer object.
Args:
velocity: The MIDI note velocity to use.
instrument: The MIDI instrument to use.
program: The MIDI program to use.
chord_symbol_functions: ChordSymbolFunctions object with which to perform
the actual transposition of chord symbol strings.
"""
self._velocity = velocity
self._instrument = instrument
self._program = program
self._chord_symbol_functions = chord_symbol_functions
def _render_notes(self, sequence, pitches, start_time, end_time):
for pitch in pitches:
# Add a note.
note = sequence.notes.add()
note.start_time = start_time
note.end_time = end_time
note.pitch = pitch
note.velocity = self._velocity
note.instrument = self._instrument
note.program = self._program
def render(self, sequence):
# Sort text annotations by time.
annotations = sorted(sequence.text_annotations, key=lambda a: a.time)
prev_time = 0.0
prev_figure = NO_CHORD
for annotation in annotations:
if annotation.time >= sequence.total_time:
break
if annotation.annotation_type == CHORD_SYMBOL:
if prev_figure != NO_CHORD:
# Render the previous chord.
pitches = self._chord_symbol_functions.chord_symbol_midi_pitches(
prev_figure)
self._render_notes(sequence=sequence,
pitches=pitches,
start_time=prev_time,
end_time=annotation.time)
prev_time = annotation.time
prev_figure = annotation.text
if (prev_time < sequence.total_time and
prev_figure != NO_CHORD):
# Render the last chord.
pitches = self._chord_symbol_functions.chord_symbol_midi_pitches(
prev_figure)
self._render_notes(sequence=sequence,
pitches=pitches,
start_time=prev_time,
end_time=sequence.total_time)
class SingleChordEncoderDecoder(object):
"""An abstract class for encoding and decoding individual chords.
"""
__metaclass__ = abc.ABCMeta
@abc.abstractproperty
def num_classes(self):
"""The number of distinct chord encodings.
Returns:
An int, the range of ints that can be returned by self.encode_chord.
"""
pass
@abc.abstractmethod
def encode_chord(self, figure):
"""Convert from a chord symbol string to a chord encoding integer.
Args:
figure: A chord symbol string representing the chord.
Returns:
An integer representing the encoded chord, in range [0, self.num_classes).
"""
pass
@abc.abstractmethod
def decode_chord(self, index):
"""Convert from a chord encoding integer to a chord symbol string.
Args:
index: The encoded chord, an integer in the range [0, self.num_classes).
Returns:
A chord symbol string representing the decoded chord.
"""
pass
class MajorMinorEncoderDecoder(SingleChordEncoderDecoder):
"""Encodes chords as root + major/minor, with zero index for "no chord".
Encodes chords as follows:
0: "no chord"
1-12: chords with a major triad, where 1 is C major, 2 is C# major, etc.
13-24: chords with a minor triad, where 13 is C minor, 14 is C# minor, etc.
"""
# Mapping from pitch class index to name. Eventually this should be defined
# more globally, but right now only `decode_chord` needs it.
_PITCH_CLASS_MAPPING = ['C', 'C#', 'D', 'E-', 'E', 'F',
'F#', 'G', 'A-', 'A', 'B-', 'B']
def __init__(self, chord_symbol_functions=
chord_symbols_lib.ChordSymbolFunctions.get()):
"""Initialize the MajorMinorEncoderDecoder object.
Args:
chord_symbol_functions: ChordSymbolFunctions object with which to perform
the actual transposition of chord symbol strings.
"""
self._chord_symbol_functions = chord_symbol_functions
@property
def num_classes(self):
return 2 * NOTES_PER_OCTAVE + 1
def encode_chord(self, figure):
if figure == NO_CHORD:
return 0
root = self._chord_symbol_functions.chord_symbol_root(figure)
quality = self._chord_symbol_functions.chord_symbol_quality(figure)
if quality == chord_symbols_lib.CHORD_QUALITY_MAJOR:
return root + 1
elif quality == chord_symbols_lib.CHORD_QUALITY_MINOR:
return root + NOTES_PER_OCTAVE + 1
else:
raise ChordEncodingException('chord is neither major nor minor: %s'
% figure)
def decode_chord(self, index):
if index == 0:
return NO_CHORD
elif index - 1 < 12:
# major
return self._PITCH_CLASS_MAPPING[index - 1]
else:
# minor
return self._PITCH_CLASS_MAPPING[index - NOTES_PER_OCTAVE - 1] + 'm'
class ChordsEncoderDecoder(events_lib.EventsEncoderDecoder):
"""An abstract class for translating between chords and model data.
When building your dataset, the `encode` method takes in a chord progression
and returns a SequenceExample of inputs and labels. These SequenceExamples
are fed into the model during training and evaluation.
During generation, the `get_inputs_batch` method takes in a list of the
current chord progressions and returns an inputs batch which is fed into the
model to predict what the next chord should be for each progression. The
`extend_event_sequences` method takes in the list of chord progressions
and the softmax returned by the model and extends each progression by one
step by sampling from the softmax probabilities. This loop
(`get_inputs_batch` -> inputs batch is fed through the model to get a
softmax -> `extend_event_sequences`) is repeated until the generated
chord progressions have reached the desired length.
"""
__metaclass__ = abc.ABCMeta
@abc.abstractmethod
def events_to_input(self, events, position):
"""Returns the input vector for the chord event at the given position.
Args:
events: A ChordProgression object.
position: An integer event position in the chord progression.
Returns:
An input vector, a self.input_size length list of floats.
"""
pass
@abc.abstractmethod
def events_to_label(self, events, position):
"""Returns the label for the chord event at the given position.
Args:
events: A ChordProgression object.
position: An integer event position in the chord progression.
Returns:
A label, an integer in the range [0, self.num_classes).
"""
pass
@abc.abstractmethod
def class_index_to_event(self, class_index, events):
"""Returns the chord event for the given class index.
This is the reverse process of the self.events_to_label method.
Args:
class_index: An integer in the range [0, self.num_classes).
events: A ChordProgression object.
Returns:
An chord progression event value, the chord symbol figure string.
"""
pass
def transpose_and_encode(self, chords, transpose_amount):
"""Returns a SequenceExample for the given chord progression.
Args:
chords: A ChordProgression object.
transpose_amount: The number of half steps to transpose the chords.
Returns:
A tf.train.SequenceExample containing inputs and labels.
"""
chords.transpose(transpose_amount)
return self._encode(chords)