The instruments being layered on top of each other was a brilliant idea. Because the game had very simple and concise "escort" missions, they did not feel like a chore, and added a neat little story element to the game. Once all instruments were collected, I think the game became a little hard and dependent on luck. The problem was that sometimes, no matter what you did, there was no way to stop all the bats that were attacking the orchestra. On my first playthrough, this really bit me hard, and I failed because of it. I understand that its a tall order for a jam game, but the end sequence really needs some sort of smarter bat spawning system to make it feel fair.
Overall, it was a cute little game, and I liked it :)