An earworm. A piece of music that goes around inside your head sometimes constantly what won't go away. I have one most days at some point. Often totally at random. Sometimes it's something I like. Other times something I hate. Sometimes something I can't quite place. Usually just a few lines or short musical passage. Nearly always annoying. (Even 10 -20 seconds of HBTS on repeat will irritate me)
Anyway my earworm today which has prompted this is, SOS Abba. 😭