Background noises.

You gotta listen to background noise sometimes too.  Sometimes they sync up into a perfect rhythm like in this example above.  I know its an accident and highly tenuous but come on there is a steady rhythm of what sounds like an old clock and a mechanical hum along with purring that proves unusual but listenable. 

This guy has a blog dedicated to his cats its called Kagoneko or cat basket and is possibly the cutest thing ever.  Cats in baskets, cats balancing fruit and cats just being cats.  Enjoy.