[ntoshev]

What if you tried to transcribe the music solely from Fourier transform of the audio source? I expect the piano has an abundance of harmonics, but there should be some way to distinguish them from the keys. Hasn't someone done it already?

[gtani]

i've seen NNLS/chroma referenced in a few places, like the chordify papers:

http://isophonics.net/nnls-chroma

Here's chordify: http://ismir2012.ismir.net/event/papers/295_ISMIR_2012.pdf

That conference has great references but unfortunately hasn't been repeated since 2012 http://www.ismir.net/proceedings/index.php

[raverbashing]

It's certainly hard

However, this case would be one of the best cases for it, it's a single instrument, and you could make a careful recording out of it