diff --git a/pychord/chord.py b/pychord/chord.py index 385c144..e534a23 100644 --- a/pychord/chord.py +++ b/pychord/chord.py @@ -59,22 +59,34 @@ def __ne__(self, other): return not self.__eq__(other) @classmethod - def from_note_index(cls, note: int, quality: str, scale: str, diatonic: bool = False) -> 'Chord': - """ Create a Chord from note index in a scale + def from_note_index( + cls, + note: int, + quality: str, + scale: str, + diatonic: bool = False, + chromatic: int = 0, + ) -> "Chord": + """Create a Chord from note index in a scale Chord.from_note_index(1, "", "Cmaj") returns I of C major => Chord("C") Chord.from_note_index(3, "m7", "Fmaj") returns IIImin of F major => Chord("Am7") Chord.from_note_index(5, "7", "Amin") returns Vmin of A minor => Chord("E7") - - :param note: Note index in a Scale I, II, ..., VIII - :param quality: Quality of a chord (m7, sus4, ...) - :param scale: Base scale (Cmaj, Amin, F#maj, Ebmin, ...) - :param diatonic: Adjust certain chord qualities according to the scale + Chord.from_note_index(2, "", "Cmaj") returns II of C major => Chord("D") + Chord.from_note_index(2, "m", "Cmaj") returns IImin of C major => Chord("Dm") + Chord.from_note_index(2, "", "Cmaj", diatonic=True) returns IImin of C major => Chord("Dm") + Chord.from_note_index(2, "", "Cmin", chromatic=-1) returns bII of C minor => Chord("Db") + + :param note: Scale degree of the chord's root (1-7) + :param quality: Quality of the chord (e.g. m7, sus4) + :param scale: Base scale (e.g. Cmaj, Amin, F#maj, Ebmin) + :param diatonic: If True, chord quality is determined using the base scale (overrides :param quality) + :param chromatic: Lower or raise the scale degree (and all notes of the chord) by semitone(s) """ if not 1 <= note <= 8: raise ValueError(f"Invalid note {note}") relative_key = RELATIVE_KEY_DICT[scale[-3:]][note - 1] - root_num = NOTE_VAL_DICT[scale[:-3]] + root_num = NOTE_VAL_DICT[scale[:-3]] + chromatic root = VAL_NOTE_DICT[(root_num + relative_key) % 12][0] scale_degrees = RELATIVE_KEY_DICT[scale[-3:]] @@ -87,6 +99,7 @@ def from_note_index(cls, note: int, quality: str, scale: str, diatonic: bool = F # adjust the chord to its root position (as a stack of thirds), # then set the root to 0 + # e.g. (9, 0, 4) -> [0, 3, 7] def get_diatonic_chord(chord): uninverted = [] for note in chord: