You miss the point I think. The OP isn't talking about playing music on an external source that he can physically hear (as can anyone else who is close enough). He's talking about music that comes unbidden into his head (that only he can hear) usually as a reaction to what he sees.
Originally Posted by sun of sand
While this isn't exactly rare, it's also not exactly common. So if you don't hear music when you are photographing, you are probably in the majority.
So maybe this thread ain't about you. That's not a bad thing. It's just a thing.