source: python/lib/aubio/midiconv.py @ 60583a3

# -*- coding: utf-8 -*-
""" utilities to convert midi note number to and from note names """

__all__ = ['note2midi', 'midi2note', 'freq2note']

import sys
py3 = sys.version_info[0] == 3
if py3:
    str_instances = str
    int_instances = int
else:
    str_instances = (str, unicode)
    int_instances = (int, long)

def note2midi(note):
    " convert note name to midi note number, e.g. [C-1, G9] -> [0, 127] "
    _valid_notenames = {'C': 0, 'D': 2, 'E': 4, 'F': 5, 'G': 7, 'A': 9, 'B': 11}
    _valid_modifiers = {
            u'𝄫': -2,                        # double flat
            u'♭': -1, 'b': -1, '\u266d': -1, # simple flat
            u'♮': 0, '\u266e': 0, None: 0,   # natural
            '#': +1, u'♯': +1, '\u266f': +1, # sharp
            u'𝄪': +2,                        # double sharp
            }
    _valid_octaves = range(-1, 10)
    if not isinstance(note, str_instances):
        raise TypeError("a string is required, got %s (%s)" % (note, str(type(note))))
    if len(note) not in range(2, 5):
        raise ValueError("string of 2 to 4 characters expected, got %d (%s)" \
                         % (len(note), note))
    notename, modifier, octave = [None]*3

    if len(note) == 4:
        notename, modifier, octave_sign, octave = note
        octave = octave_sign + octave
    elif len(note) == 3:
        notename, modifier, octave = note
        if modifier == '-':
            octave = modifier + octave
            modifier = None
    else:
        notename, octave = note

    notename = notename.upper()
    octave = int(octave)

    if notename not in _valid_notenames:
        raise ValueError("%s is not a valid note name" % notename)
    if modifier not in _valid_modifiers:
        raise ValueError("%s is not a valid modifier" % modifier)
    if octave not in _valid_octaves:
        raise ValueError("%s is not a valid octave" % octave)

    midi = 12 + octave * 12 + _valid_notenames[notename] + _valid_modifiers[modifier]
    if midi > 127:
        raise ValueError("%s is outside of the range C-2 to G8" % note)
    return midi

def midi2note(midi):
    " convert midi note number to note name, e.g. [0, 127] -> [C-1, G9] "
    if not isinstance(midi, int_instances):
        raise TypeError("an integer is required, got %s" % midi)
    if midi not in range(0, 128):
        raise ValueError("an integer between 0 and 127 is excepted, got %d" % midi)
    _valid_notenames = ['C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B']
    return _valid_notenames[midi % 12] + str(int(midi / 12) - 1)

def freq2note(freq):
    " convert frequency in Hz to nearest note name, e.g. [0, 22050.] -> [C-1, G9] "
    from aubio import freqtomidi
    return midi2note(int(freqtomidi(freq)))