Function substitute_major_for_minor

mingus/core/progressions.py:329–360

Substitute major chords for their minor equivalent. 'M' and 'M7' suffixes recognized, and ['I', 'IV', 'V'] if there is no suffix. Examples: >>> substitute_major_for_minor(['I'], 0) ['VI'] >>> substitute_major_for_minor(['VM7'], 0) ['IIIm7']

(progression, substitute_index, ignore_suffix=False)

def substitute_major_for_minor(progression, substitute_index, ignore_suffix=False):
    """Substitute major chords for their minor equivalent.

    'M' and 'M7' suffixes recognized, and ['I', 'IV', 'V'] if there is no
    suffix.

    Examples:
    >>> substitute_major_for_minor(['I'], 0)
    ['VI']
    >>> substitute_major_for_minor(['VM7'], 0)
    ['IIIm7']
    """
    (roman, acc, suff) = parse_string(progression[substitute_index])
    res = []

    # Major to minor substitution
    if (
        suff == "M"
        or suff == "M7"
        or suff == ""
        and roman in ["I", "IV", "V"]
        or ignore_suffix
    ):
        n = skip(roman, 5)
        a = interval_diff(roman, n, 9) + acc
        if suff == "M" or ignore_suffix:
            res.append(tuple_to_string((n, a, "m")))
        elif suff == "M7" or ignore_suffix:
            res.append(tuple_to_string((n, a, "m7")))
        elif suff == "" or ignore_suffix:
            res.append(tuple_to_string((n, a, "")))
    return res


def substitute_diminished_for_diminished(