I have an idea for a program I wish to write, but it requires a way to convert musical audio (single guitar, at first approximation) to notes (e.g., OCR/speech-recognition for music).

Google found IntelliScore, but although it advertises more power that I need (several instruments), it is proprietary, and I’m looking for something that is free and GPL-compatible.

Are there any free/GPL programs or libraries that can do this?

2 Answers

There’s Notey. It can detect notes and transcribe them on screen. It’s GPL, so you should be able to extract and adapt the detection/conversion routines.

Another options is music scribe kit which:

Is a toolkit for transcribing a music audio file to common music notation. This is done by manually annotating a spectrogram or something similar and converting it to a MIDI file and to a abc music notation file.

The proprietary program Transcribe! has an extensive list of other music-transcription tools, including some that are open-source. You can also check SourceForge for other open-source music-transcription programs.

Google recommended waon.

Originally on I had it compile on Xubuntu 18.04, including gtk-based gui.

What is waon

WaoN is a Wave-to-Notes transcriber, that is, the inverse of timidity by Tuukka Toivonen (and its descendants timidity++). (...) My original intention is to pick up voicing of harmony from sound of my favorite pianists. (...)

Currently, WaoN contains three programs:

waon: transcriber (wav-to-mid converter)
pv: phase vocoder for time-streching and pitch-shifting
gwaon: GUI for waon and pv

WaoN is released under the GNU General Public License.

Where to find source code

CVS is dated and sourceforge is phasing out. I converted the CVS-based history to git and re-hosted it on .

Any options?

Here the summary of options the excutable provides.

 ./waon --help
WaoN - a Wave-to-Notes transcriber, Version 0.10
Copyright (C) 1998-2007 Kengo Ichiki <>
Web:
WaoN is a Wave-to-Notes transcriber,
that is, a converter from sound file to midi file.
Usage: ./waon [option ...]
Options: -h --help print this help. -v, --version print version information.
OPTIONS FOR FILES -i --input input wav file (default: stdin) -o --output output mid file (default: 'output.mid') options -i and -o have argument '-' as stdin/stdout -p --patch patch file (default: no patch)
FFT OPTIONS -n sampling number from WAV in 1 step (default: 2048) -w --window 0 no window 1 parzen window 2 welch window 3 hanning window (default) 4 hamming window 5 blackman window 6 steeper 30-dB/octave rolloff window
READING WAV OPTIONS -s --shift shift number from WAV in 1 step (default: 1/4 of the value in -n option)
PHASE-VOCODER OPTIONS -nophase don't use phase diff to improve freq estimation. (default: use the correction)
NOTE SELECTION OPTIONS -c --cutoff log10 of cut-off ratio to scale velocity of note (default: -5.0) -r --relative log10 of cut-off ratio relative to the average. (default: no relative cutoff = absolute cutoff with the value in -c option) -k --peak peak threshold for note-on, which ranges [0,127] (default: 128 = no peak-search = search only first on-event) -t --top top note [midi #] (default: 103 = G7) -b --bottom bottom note [midi #] (default: 28 = E1) Here middle C (261 Hz) = C4 = midi 60. Midi # ranges [0,127]. -a --adjust adjust-pitch param, which is suggested by WaoN after analysis. unit is half-note, that is, +1 is half-note up, and -0.5 is quater-note down. (default: 0)
DRUM-REMOVAL OPTIONS -psub-n number of averaging bins in one side. that is, for n, (i-n,...,i,...,i+n) are averaged (default: 0) -psub-f factor to the average, where the power is modified as p[i] = (sqrt(p[i]) - f * sqrt(ave[i]))^2 (default: 0.0)
OCTAVE-REMOVAL OPTIONS -oct factor to the octave removal, where the power is modified as p[i] = (sqrt(p[i]) - f * sqrt(oct[i]))^2 (default: 0.0)