Sometimes I wake up with a melody in my head, one I don't recall ever hearing before. So apparently my brain is composing while I sleep. Sometimes I go to the computer and enter the tune in Noteworthy Composer to save it for the future.

The music seems to have no connection to dreams. It's just there, as sound, when I wake up.

I understand that some people hear voices when they wake up or go to sleep, and the music I hear may be similar to that. (Once I read that hearing voices in your head is a symptom of schizophrenia EXCEPT if you hear them while falling asleep or waking up.)