I got stuck in this spot in the fourth (fifth) level?
I'm really, really in love with this music, and I think the slowness fo the character gives you a reason to try to solve the puzzles instead of just doing trial and error. I also think the slowness goes along well with the music.
However, I tried for a long time to notice a change in the music associated with each door, and i didn't hear any, so i did end up just guessing.