Have you ever gone through an entire day, and then realized, only toward the end of the day, that all day long a particular song had been running through your head? That happened to me today.
The funny thing is that it has happened to me lots of times before. And I generally don’t realize, until the end of the day, that I have been playing the same song in my head for hours on end.
I suspect that this may be a widespread phenomenon. And I also suspect that it’s a sort of “pearl in the oyster” sort of thing.
In other words, somebody says a random phrase, or you have a particular experience, which gets a bit of remembered song lyric into your head. You don’t really take note of that initial experience, but your brain latches on to that moment, like the grain of sand in an oyster, and builds upon it.
Before you know it, the song is playing in your head. Except you don’t realize, until much later in the day, that you’ve been playing, on an endless loop, that song in your head.