I love the concept, but it definitely could need a clear goal. Right now it's more of a sandbox playground than it is a game, but that isn't necessarily a bad thing. It would be fun if you could somehow create the rhythm/melody yourself on the given instrument by doing interactions and that would eventually turn into a song. The tune would naturally have to follow a set pattern, but I could definitely smell some potential here.
The art and music was super good though, good job.