Diana, what you are describing is exactly what I'm experiencing. America the Beautiful, Silent Night, The Caissons go Rolling Along, and others. Who knows why the songs that repeat over and over are stuck in my head. They seem to be ones I knew from childhood. Often just certain phrases of the song will repeat. They are always there, only disappearing when I'm distracted or fully engaged in something else. I did some research and apparently this is very common. I've had this condition for a looooong time.