You spent --- what I'd assume would be several k$ from prices found online --- to buy a self-playing piano, and are now asking if you can release the tools to have it play the music of your choosing? IMHO the fact that you even had to think about asking if you could do this is everything that's wrong with society today. IANAL but as long as you aren't releasing something that's copyrighted from the original code, or violating some patent, there shouldn't be anything to worry about.

"It's better to ask for forgiveness than permission", as the saying goes. ;-)