My mind has tottally made up a slew of music I can't remember when I wake up...and its usually pretty good. Which is too bad I can't remember it...
But the most notable thing that happened to me once was that I fell asleep with headphones on with a song I liked on repeat and during my dream I heard music but it wasn't the SAME music that was still playing when I woke up. My brain made up a bunch of crazy awesome music that had nothing to do with what I was physically hearing when I went to sleep.