Very cool game! As a musician, i loved the concept and even it is not how music is played, it is creative and i like!
The piano notes's sound is nice, but i think they could be more legato (played smoothly together).
I love how you put the time to put real melodies, not just random notes. I approve the Ode To Joy!!!
Overall, a very nice game, very creative and you definetely need to further develop it! Nice work!