I like coffee*

I'm at uni, drinking coffee and listening to music on my mp3 player while waiting for a lecture to start. There's a guy sitting near me who's reading and also listening to his mp3 player. He seems to be slightly dancing or moving his head and occasionally his upper body in time with the music that I can't hear. I wonder if he's aware that he's doing it or if it's a subconscious action, and I'm also curious as to what he's listening to. It's evident that some songs or sections have more of an effect that others, and his mini-dancing isn't in time with the music currently playing on my player.

* Yes, I'm aware that the title doesn't have much to do with the content of this post but it's true, I like coffee.