update: I tried with all my songs and yes I know it doesn't work with every song. I just think it works if you play the song on time or it works with some sort of upbeat song. But yea, it doesn't work perfectly like you would expect.
This is such an amazing idea. I've already thought of two things it might be useful for: a) No headphone cords when running. b) No headphone cords if you fall asleep (just in case they get wrapped around your neck)