I have music stuck in my head more or less constantly. It's never bothered, and I'm kind of surprised to find all the remedies suggested here. For me, instrumental music is no different from vocal music. It can be a riff from a solo, a chord change, an interesting timbre, or pretty much any sound. Sometimes I think they're not from songs that have yet been recorded. Just the imagination of sounds that turn over and over. I've always kind of liked it. I'm a musician myself, and I think it helps me think of old music in new ways.