I have music running in my head most of the time, at least in the background unless I’m concentrating deeply on something. I’m also a musician and the best way I can describe it is that the music I’m hearing in my head somehow comes out of my instrument.

I do. I can "play it back" in my head, with full music/lyrics/chords/etc.

I do and just asked around among friends. Everyone did.

Most I think, especially among musicians, which makes the GP fascinating to me!

Can you literally hear music in a dream have you never had an auditorial hallucination?