This is just another reason why I think Inception is a fantastic movie. I'm going to write about it later this week, but here's a little tidbit for those that have already seen it. There aren't any spoiler for those who haven't seen it, but you won't really get it until you see the movie.
I love the little subtleties that Christopher Nolan throws in his movies.
This part is a spoiler though. Stop reading if you haven't seen it.
The music thing totally makes sense. In the movie, time slows down when they're in the dream, so when they're listening to that music through the headphones, it would be slowed down like that.