Function to_chords

mingus/core/progressions.py:42–95

Convert a list of chord functions or a string to a list of chords. Examples: >>> to_chords(['I', 'V7']) [['C', 'E', 'G'], ['G', 'B', 'D', 'F']] >>> to_chords('I7') [['C', 'E', 'G', 'B']] Any number of accidentals can be used as prefix to augment or diminish; for example

(progression, key="C")

def to_chords(progression, key="C"):
    """Convert a list of chord functions or a string to a list of chords.

    Examples:
    >>> to_chords(['I', 'V7'])
    [['C', 'E', 'G'], ['G', 'B', 'D', 'F']]
    >>> to_chords('I7')
    [['C', 'E', 'G', 'B']]

    Any number of accidentals can be used as prefix to augment or diminish;
    for example: bIV or #I.
    
    All the chord abbreviations in the chord module can be used as suffixes;
    for example: Im7, IVdim7, etc.
    
    You can combine prefixes and suffixes to manage complex progressions:
    #vii7, #iidim7, iii7, etc.
    
    Using 7 as suffix is ambiguous, since it is classicly used to denote the
    seventh chord when talking about progressions instead of just the
    dominant seventh chord. We have taken the classic route; I7 will get
    you a major seventh chord. If you specifically want a dominanth seventh,
    use Idom7.
    """
    if isinstance(progression, six.string_types):
        progression = [progression]
    result = []
    for chord in progression:
        # strip preceding accidentals from the string
        (roman_numeral, acc, suffix) = parse_string(chord)

        # There is no roman numeral parsing, just a simple check. Sorry to
        # disappoint. warning Should throw exception
        if roman_numeral not in numerals:
            return []

        # These suffixes don't need any post processing
        if suffix == "7" or suffix == "":
            roman_numeral += suffix

            # ahh Python. Everything is a dict.
            r = chords.__dict__[roman_numeral](key)
        else:
            r = chords.__dict__[roman_numeral](key)
            r = chords.chord_shorthand[suffix](r[0])

        while acc < 0:
            r = [notes.diminish(x) for x in r]
            acc += 1
        while acc > 0:
            r = [notes.augment(x) for x in r]
            acc -= 1
        result.append(r)
    return result


def determine(chord, key, shorthand=False):