You can create music in the recent versions of Bitsy but it's extremely buggy so for my previous game, which i mentioned in another comment, I initially tried and then gave up after I saw how the problems disrupted the gameplay. In older versions of Bitsy (or alternatively) you can add it with a hack that I believe works quite well but I just didn't remotely have the time to compose something. I would love to - I always want to add music to my games - but when it's a jam situation and I'm working solo it just ends up being impossible, sadly.
Thanks for saying such kind words about the game. I'm glad you enjoyed it.