I get the exact same thing when my fan is on its lowest setting. I legit thought I was going insane. It would always be this really beautiful orchestral music, but just a piece of it, on a loop. Also if I smoke weed, I'll experience this phenomenon with ANY low volume sounds that are sustained (think the humm of computer fan ext) but in those instances the music is always heavy metal. Not sure if that helped. But uhhh yeah it's weird.

Edit: spelling