There is an interesting article in the New York Times about musical hallucinations. Here's a bit of it:
Seven years ago Reginald King was lying in a hospital bed recovering from bypass surgery when he first heard the music. It began with a pop tune, and others followed. Mr. King heard everything from cabaret songs to Christmas carols. "I asked the nurses if they could hear the music, and they said no," said Mr. King, a retired sales manager in Cardiff, Wales.
...Each day, the music returns. "They're all songs I've heard during my lifetime," said Mr. King, 83. "One would come on, and then it would run into another one, and that's how it goes on in my head. It's driving me bonkers, to be quite honest."
Last year, Mr. King was referred to Dr. Victor Aziz, a psychiatrist at St. Cadoc's Hospital in Wales. Dr. Aziz explained to him that there was a name for his experience: musical hallucinations. Dr. Aziz belongs to a small circle of psychiatrists and neurologists who are investigating this condition. They suspect that the hallucinations experienced by Mr. King and others are a result of malfunctioning brain networks that normally allow us to perceive music.
...Musical hallucinations were invading people's minds long before they were recognized as a medical condition. "Plenty of musical composers have had musical hallucinations," Dr. Aziz said. Toward the end of his life, for instance, Robert Schumann wrote down the music he hallucinated; legend has it that he said he was taking dictation from Schubert's ghost.
...Mr. King's experience was typical for people experiencing musical hallucinations. Patients reported hearing a wide variety of songs, among them "Don't Cry for Me Argentina" and "Three Blind Mice."
Pretty weird. I remember hearing music in my head as a kid when I spent the night at my grandparents' house. It sounded just like a radio to me, but I haven't experienced that since. The article says that people who have these hallucinations are typically understimulated, and that was certainly the case for me when I was spending the night at my grandparents. Not that I didn't enjoy watching the Carter Family and going to bed at 7:30, but still. Also, I was amused to see that the Times slipped in yet another reference to the iPod, this time in the title of the article. Those guys just can't give Apple too much free publicity.