music21 VS nnls-chroma

I chose Python as a programming language here because, as you could probably guess, there are myriads of libraries in Python for working with music. I found mingus to be the simplest for working with guitar chords and music21 for generating the piano score. It might be possible though to do everything with music21 only, because it's extremely powerful, but I found mixing the two libraries to be easier than implementing the functionality I needed from mingus with music21.

If you are interested in doing anything with Python, be sure to check out Music21, which has a lot of cool features — including doing twelve-tone matrix stuff like this — built-in.

http://web.mit.edu/music21/ Music21 documentation.

It's definitely a viable possiblity, and there's quite a few companeis already doing it. If you want to explore doing it yourself, I'd check out https://web.mit.edu/music21/ and build some basic models using LSTM etc. to have some fun using open source MIDI data sets like https://magenta.tensorflow.org/datasets/maestro .

A little manual, but music21[0] can do the analysis!

[0]: http://web.mit.edu/music21/

There's no universally accepted term for the latter concept that I know of. For example, the music21 music processing library calls the general class that includes notes, chords and rests Music21Objects, and you'd think they'd call them something better if they could.

This Python toolkit has support for analyzing folk tunes. https://web.mit.edu/music21/

(define-public music21 (package ... (build-system python-build-system) (arguments `(#:phases (modify-phases %standard-phases (replace 'check (lambda* (#:key tests? inputs outputs #:allow-other-keys) (when tests? (add-installed-pythonpath inputs outputs) ;; See: https://github.com/cuthbertLab/music21/issues/1164 (invoke "python" "-m" "music21.stream.tests"))))))) ...))

There are various commercial offerings that do this, including Chordify and Capo.

If you want source code, consider the Chordino plugin (http://www.isophonics.net/nnls-chroma, C++ code at https://github.com/c4dm/nnls-chroma) which you can use in Sonic Visualiser (https://www.sonicvisualiser.org/).

There is a reference for the Chordino method in the page linked above, but roughly it's not that far from the description of the parent poster - a non-negative least-squares method produces a frame-by-frame semitone-scaled decomposition which is then matched against templates and turned into a chord sequence using a hidden Markov model.