src/birdears/scale.py
from . import DIATONIC_FORMS
from .note_and_pitch import Pitch
from .note_and_pitch import Chord
from .note_and_pitch import get_pitch_by_number
from itertools import cycle
# https://docs.python.org/3/reference/datamodel.html#emulating-container-types
class ScaleBase(list):
def __init__(self):
pass
class DiatonicScale(ScaleBase):
"""Builds a musical diatonic scale.
Attributes:
scale (array_type): The array of notes representing the scale.
"""
def __init__(self, tonic='C', mode='major', octave=4, n_octaves=1,
descending=False, dont_repeat_tonic=False):
"""Returns a diatonic scale from tonic and mode.
Args:
tonic (str): The note which the scale will be built upon.
mode (str): The mode the scale will be built upon.
('major' or 'minor')
octave (int): The scientific octave the scale will be built upon.
n_octaves (int): The number of octaves the scale will contain.
descending (bool): Whether the scale is descending.
dont_repeat_tonic (bool): Whether to skip appending the last
note (octave) to the scale.
"""
super(DiatonicScale, self).__init__()
self.tonic = Pitch(note=tonic, octave=octave)
self.mode = mode
self.direction = "Ascending" if not descending else "Descending"
self.is_descending = descending
self.n_octaves = n_octaves
diatonic_mode = DIATONIC_FORMS[mode]
form_length = len(diatonic_mode)
direction = +1 if not descending else -1
repeat_tonic = 0 - dont_repeat_tonic # 0 (repeat) or -1
if descending:
diatonic_mode = diatonic_mode[::-1]
diatonic_loop = cycle(diatonic_mode)
scale = list()
self.append(self.tonic)
pitch_num = int(self[0])
for i in range((form_length * n_octaves) + repeat_tonic):
step = next(diatonic_loop)
pitch_num += step * direction
accident = ('flat' if (('b' in tonic) or (tonic == 'F'))
else 'sharp')
pitch = get_pitch_by_number(numeric=pitch_num, accident=accident)
scale.append(pitch)
self.extend(scale)
# FIXME: aybe ake this a function
def get_triad(self, index=0, degree=None):
"""Returns an array with notes from a scale's triad.
Args:
index (int): triad index (eg.: 0 for 1st degree triad.)
degree (int): Degree of the scale. If provided, overrides the
`index` argument. (eg.: `1` for the 1st degree triad.)
Returns:
An array with three pitches, one for each note of the triad.
"""
tonic = self.tonic
mode = self.mode
diatonic = DiatonicScale(tonic=tonic.note, mode=mode,
octave=tonic.octave, n_octaves=2,
descending=False, dont_repeat_tonic=False)
if degree:
index = degree - 1
form = [0, 2, 4]
triad = [diatonic[index+note] for note in form]
chord = Chord(triad)
return chord
def __repr__(self):
repr = "<DiatonicScale {tonic} {mode} {direction} {first}-{to} " \
"({octaves} octaves)>" \
.format(tonic=str(self[0].note),
mode=self.mode.capitalize(),
direction=self.direction.capitalize(),
first=str(self[0]),
to=str(self[-1]), octaves=int(len(self)/8))
return repr
def __str__(self):
return str(list(self))
class ChromaticScale(ScaleBase):
"""Builds a musical chromatic scale.
Attributes:
scale (array_type): The array of notes representing the scale.
"""
def __init__(self, tonic='C', octave=4, n_octaves=1, descending=False,
dont_repeat_tonic=False):
"""Returns a chromatic scale from tonic.
Args:
tonic (str): The note which the scale will be built upon.
octave (int): The scientific octave the scale will be built upon.
n_octaves (int): The number of octaves the scale will contain.
descending (bool): Whether the scale is descending.
dont_repeat_tonic (bool): Whether to skip appending the last
note (octave) to the scale.
"""
super(ChromaticScale, self).__init__()
# global CHROMATIC_SHARP, CHROMATIC_FLAT
self.tonic = Pitch(tonic, octave)
self.direction = "Ascending" if not descending else "Descending"
self.is_descending = descending
self.n_octaves = n_octaves
direction = +1 if not descending else -1
tonic_pitch_num = int(self.tonic)
repeat_tonic = not dont_repeat_tonic # 1 or 0
accident = 'flat' if (('b' in tonic) or (tonic == 'F')) else 'sharp'
scale = [get_pitch_by_number(numeric=tonic_pitch_num + (i*direction),
accident=accident)
for i in range((12 * n_octaves) + repeat_tonic)]
self.extend(scale)
def get_triad(self, mode, index=0, degree=None):
"""Returns an array with notes from a scale's triad.
Args:
mode (str): Mode of the scale (eg. 'major' or 'minor')
index (int): Triad index (eg.: 0 for 1st degree triad.)
degree (int): Degree of the scale. If provided, overrides the
`index` argument. (eg.: `1` for the 1st degree triad.)
Returns:
A list with three pitches (str), one for each note of the triad.
"""
tonic = self.tonic
diatonic = DiatonicScale(tonic=tonic.note, mode=mode,
octave=tonic.octave, n_octaves=2,
descending=False, dont_repeat_tonic=False)
if degree:
index = degree - 1
form = [0, 2, 4]
triad = [diatonic[index+note] for note in form]
chord = Chord(triad)
return chord