Function substitute_harmonic

mingus/core/progressions.py:258–290

Do simple harmonic substitutions. Return a list of possible substitions for progression[substitute_index]. If ignore_suffix is set to True the suffix of the chord being substituted will be ignored. Otherwise only progressions without a suffix, or with suffix '7' will be substituted.

(progression, substitute_index, ignore_suffix=False)

def substitute_harmonic(progression, substitute_index, ignore_suffix=False):
    """Do simple harmonic substitutions. Return a list of possible substitions
    for progression[substitute_index].

    If ignore_suffix is set to True the suffix of the chord being
    substituted will be ignored. Otherwise only progressions without a
    suffix, or with suffix '7' will be substituted.

    The following table is used to convert progressions:
    || I || III ||
    || I || VI ||
    || IV || II ||
    || IV || VI ||
    || V || VII ||
    """
    simple_substitutions = [
        ("I", "III"),
        ("I", "VI"),
        ("IV", "II"),
        ("IV", "VI"),
        ("V", "VII"),
    ]
    res = []
    (roman, acc, suff) = parse_string(progression[substitute_index])
    if suff == "" or suff == "7" or ignore_suffix:
        for subs in simple_substitutions:
            r = subs[1] if roman == subs[0] else None
            if r == None:
                r = subs[0] if roman == subs[1] else None
            if r != None:
                suff = suff if suff == "7" else ""
                res.append(tuple_to_string((r, acc, suff)))
    return res


def substitute_minor_for_major(progression, substitute_index, ignore_suffix=False):