I've been a musician for almost a decade now. I can tell you I occasionally get the same thing. I play mostly by ear, so my reading is lacking. I can DO it, just not as fast as my friends.

A couple of times I've had sheet music in my dreams. I've been remembering a little bit of it at a time, so I'm about 3/5 of the way through the music written down here in the real. I know it's the same music, because the melody is omnipresent throughout my dream.

How epic is that? We're music geeks!