My PDoc referred to it as Musical Hallucinosis but I actually think that is the same as Musical Ear which is I believe a form of tinnitus where you hear music externally.

What I have is a song or another playing in my head over and over, it changes depending on outside influences ... for example I could have ( as I do now ) the theme tune to a bond movie going through my head. Now I don't really know the tune so it's only the bits that I do played over and over again on repeat, and I could be reading something and see the words "All I want for christmas " and instantly it changes to all I want for christmas is my two front teeth or all i want for christmas is you. Now in the case of the bond movie I can hear it as its played, so its the actually singer and the orchestra its not my voice. where as I dont really know the song all I want for christmas so that will play in what I think is my 'inside' voice. ... does any of this make sense ??

I have No control over what is playing, it changes depending on what I see or hear. and it isnt limited to songs.

If I see a bunch of blackbirds that usually invokes the nursery rhyme " four and twenty blackbirds " over and over. Or failing that it can be a conversation I just had with someone.

I have noticed if I am walking anywhere on my own its at its worst and if I met someone on a street and have a conversation, the whole way home that conversation will play over and over again in my head.

It is utterly and totally exhausting