I've always had a thing with music. I can hear all the instruments in a song individually, I'm pretty good at picking out any tune I know on a piano, and I can remember songs I haven't heard in literally 30 years, like the instructional video from a high school French class. I somehow remember the entirety of the theme from the 80s Ricky Schroeder Sit Com Silver Spoons.
So it shouldn't be shocking that at any moment of any day, even when I'm sleeping, there's always a song playing in my head. I can imagine people finding this unbelievable, but it's absolutely true. Unless I'm actively listening to music, there's something else running in my head. Often it's so background that I don't really even notice, but it's always there. These are sometimes the earworm songs that you can't get out of your head, but they're often enough tunes that are playing on my internal soundtrack for ten minutes until I sit down at work and pop on headphones to listen to Chvrches, or Steely Dan, or Poets of the Fall.
A lot of times, I know where the song comes from. I've got a song stuck in my head because I was listening to it earlier in the day. Or I've got The Other Side stuck in my head because we watched Greatest Showman with the kids the other night. But sometimes, a song comes out of nowhere. Like, right now, why on earth do I have Piano in the Dark stuck in my head? I don't know if I've even heard that song in the past decade. Was it just playing as elevator music in the lobby or something? That's my best guess.