Naive voice extractor

here's the code backing the example i published earlier - now it's possible to extract something that resembles distinct voices from a score and base the markov chain on that. it's notable that the arpeggio feel of the original model is gone (for better or worse), leading to a radically different sound (imo) of the generated piece.

my next step would probably to come up with a way to make polyphonic composition possible (via eg one model per voice or similar, conditioning on a lead voice or so... will have to experiment, i guess)

i've provided some examples in the readme file, enjoy :)