Wonderful concept, deceptively fun as well.
Seems to have struck the perfect balance between skill and puzzle, personally leaning one direction or another would detract from the fun for me. Greatly enjoyed figuring out the puzzle aspect of this game while playing the notes to slowly form a song throughout the level. The controls are rather intuitive at first, however for some stages the controls feel a bit too spread apart. Perhaps either condensing the keys down to be closer or sticking with a specific set of keys would help with this. The gameplay loop as it is though feels amazing, having the player take control of the characters I feel would detract from the game at its core and end in a less fun final product.
All in all a lovely experience, can't wait to see where this goes!