I LOVE this concept. Best concept I've seen yet, seriously this is so damn clever I'm jealous.
my only note would be this-- have the player right click the piano block rather than hover over it to play the note because the biggest obstacle to making this game a full game is how long it takes, and the reason it takes so long is I have to go back to notes I hit to re-listen to them because when I hear a NEW tone it pushes the old one out of my head somewhat.
SO GOOD. Damn.