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key.py
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key.py
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from settings import Settings
settings = Settings()
NUMERALS = ['i', 'ii', 'iii', 'iv', 'v', 'vi', 'vii']
CHROMATIC_SCALE_NAMES = ['C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B']
CHROMATIC_SCALE_LENGTH = len(CHROMATIC_SCALE_NAMES)
# Set the octove for MIDI note 60 (middle C)
MIDDLE_OCTAVE = settings.keys['middle_octave']
MIDDLE_C = 60
START_OCTAVE = MIDDLE_OCTAVE - (MIDDLE_C // 12)
# We want to include all full scales starting at A and going to G#,
# which would end with note 116. MIDI 1.0 goes to note 127,
# but we need room for a seventh degree chord's perfect fifth,
# so let's max out at note 111 (D#).
START_NOTE, END_NOTE = 0, 116 - 5
# Calculations for chords based on the selected key
class Key:
# Create a new root "key."
# key: The root key (given as a letter in the chromatic scale)
# scale: A scale, defined as offsets to the degrees within each scale (see settings.py)
# octave: The "middle" octave as a single-digit number (most MIDI controllers assume this to be 3)
# mode: The zero-indexed mode number of the scale (e.g. 0 would be Ionian, 1 would be Dorian)
def __init__(self, key=CHROMATIC_SCALE_NAMES[0], scale=[], octave=MIDDLE_OCTAVE, mode=0, number=None):
if number:
self.octave = Key.to_octave(number)
self.key = Key.to_note(number)
else:
self.octave = octave
self.key = key
self.scale = scale
self.mode = mode
self.circle = self.scale[self.mode:] + self.scale[:self.mode]
self.circle += self.circle
self.key_offset = CHROMATIC_SCALE_NAMES.index(self.key.upper())
self.octave_offset = START_NOTE + ((self.octave - START_OCTAVE) * CHROMATIC_SCALE_LENGTH)
self.number = self.octave_offset + self.key_offset
def __third(self): return self.number + sum(self.circle[:2])
def __third_minor(self): return self.__third() - 1
def __fifth(self): return self.number + sum(self.circle[:4])
def __fifth_augmented(self): return self.__fifth() + 1
def __fifth_diminished(self): return self.__fifth() - 1
def __seventh(self): return self.number + sum(self.circle[:6])
def __seventh_minor(self): return self.__seventh() - 1
def chord_major(self): return [self.number, self.__third(), self.__fifth()]
def chord_minor(self): return [self.number, self.__third_minor(), self.__fifth()]
def chord_seventh(self): return [self.number, self.__third(), self.__fifth(), self.__seventh_minor()]
def chord_seventh_maj(self): return [self.number, self.__third(), self.__fifth(), self.__seventh()]
def chord_seventh_min(self): return [self.number, self.__third_minor(), self.__fifth(), self.__seventh_minor()]
def chord_augmented(self): return [self.number, self.__third(), self.__fifth_augmented()]
def chord_diminished(self): return [self.number, self.__third_minor(), self.__fifth_diminished()]
def chord(self, numeral):
degree = Key.to_degree(numeral)
root = self.number + sum(self.circle[:degree + 0])
third = self.number + sum(self.circle[:degree + 2])
fifth = self.number + sum(self.circle[:degree + 4])
return [root, third, fifth]
def set_scale(self, scale, mode=0):
self.__init__(self.key, scale, self.octave, mode)
def chords(self, progression):
return [self.chord(degree) for degree in progression]
def advance(self, index):
new_number = self.number + index
if new_number >=0 and new_number <= END_NOTE:
key_index = self.key_offset + index
octave = self.octave + (key_index // CHROMATIC_SCALE_LENGTH)
key = CHROMATIC_SCALE_NAMES[key_index % CHROMATIC_SCALE_LENGTH]
self.__init__(key, self.scale, octave, self.mode)
@staticmethod
def to_bassline(chord, notes=[0, 2]):
bassline = []
chord_len = len(chord) if chord else None
if not chord_len: return bassline
for offset in notes:
if chord_len > offset and chord[offset] >= 12:
bassline.append(chord[offset] - 12)
return bassline
@staticmethod
def to_name(number):
return "%s%i" % (Key.to_note(number), Key.to_octave(number))
@staticmethod
def to_octave(number):
octave_idx = (number - START_NOTE) // CHROMATIC_SCALE_LENGTH
return octave_idx + START_OCTAVE
@staticmethod
def to_note(number):
note_idx = (number - START_NOTE) % CHROMATIC_SCALE_LENGTH
return CHROMATIC_SCALE_NAMES[note_idx]
@staticmethod
def to_degree(numeral):
numeral_sanitized = ''.join(filter(lambda c: c.isalpha(), numeral.lower()))
return NUMERALS.index(numeral_sanitized)