Really great job. The music layering mechanics were a great use of the "music theme", and the combat feels good, I enjoyed it.
It feels like the classic ping pong game but with combat mechanics hehe. I tried to do something like that too with the attack/deflect mechanics and a bit based on the rhythm that is played before every enemy combo, and made a character who attacks with his violin throwing lethal notes >:D, but your method were better ;).
Anyways, good game ^^