So I played through 3 songs. The music is groovy, the notes are to the rhythm, and it is a nice challange to try and hit the notes to the beat. The interface was quite intuitive and well laid-out Now comes the harsh critical part. Don't take it personally, I don't mean to say you're a bad designer or programmer, just honest criticism helps us grow and improve. So here goes:
so, uhh you actually got a license for any of that? The music is not really yours, I'm guessing the barbie graphics aren't yours so most of the appeal is technically someone else's property. If this wasn't a jam, you would be SWIMMING in lawsuit papers. The decision to make a controller the default input method is questionable - not everybody has a PC-connected controller (I did, thankfully). Having a controller as an option would be awesome, but having it as the only way to play really limits your audience. The barbie graphics were actually cool, but very very pixelated - which would be fine, if the whole game had a pixel-art aesthetic (like a bunch of games in this jam), but since a bunch of graphics and text are a lot smoother, the pixel-ness just feels unproffesional. Having some visual feedback on pressing the buttons would benefit your game a lot, make it more satisfying. Also, hitting left and down on my controller (xbox one) was really hard, so maybe left-right would be better, or just one at a time. Lastly, the buttons which the player has to push are synced to the beat, but they don't really follow the music - they feel like 'press this random button when the beat hits'. Having multiple tracks is awesome, but you don't really benefit from it much, if the game feels the same in all levels.
Still, solid job on completing this project on your own. It's not easy having to do everything yourself.