Nice! It was a fun game. I tried really hard to get past the first level and it left me wondering: Is there another level? / another song in the game?
I have some suggestions to make it a little better.
Make it more clear if enemies hit. Sometimes it was confusing when an enemy was near and I couldn't tell if I got it or did it get through. It would also help if you make a counter showing how much life player has left.
Also make something more obvious to inform the cassette needs to be rewinded. Maybe a flashing screen, a text prompt, sound or something.