I would like to share my experience about music in my head. I don't have any musical education, but sometimes in the state of hypnogogia, I am able to hear beautiful music in my head. I understand that it just neural net somewhere in my mind create music which is based on many samples I heard before. But I was never ever able to remember it or record it, as I don't have formal musical education.

But once I stood in the house without internet, and can't sleep. I heard this music again and I was able to put it in my hand, so my fingers started to play it! So if I have a piano there I would probably be able to output my unconsciousness music out. As music is not my main interest I didn't try it again.

Another case happened at 3 after midnight on one party, when a group of 3 people including me started to sing strange but beautiful reparative song.

Conclusion: sleep deprivation affect music abilities in positive ways.