Sometimes when lying in bed and getting ready to go to sleep, without even thinking about it, its like having a radio in my head, maybe its my fillings. Anyway, sometimes I will hear symphonies, sometimes full bands with horn sections and backup female vocals etc. I dont know where it comes from or how it is being done. I will start running a simple melody through my mind and it just takes off from there, sometimes it is truly incredable but I know I am tired and cant get out of bed and if I dont just lay back and listen or some sound like the house settling happens, it
will break the spell and it comes to an end. It hasnt happened for awhile and I havent really given it any thought until I read your thread, going to have to consciencously try and get it up and going again, I used to
enjoy it alot. It was quite spotaneous and I swear just like listening to a radio. It always amazed me how creative
the mind can really be.