So, I rarely DON'T have a song in my head, and sometimes they are really freaking annoying. It usually happens because I heard some song at a grocery store or something like that, but I can also happen if I just hear a split second of a tune while fiddling with the radio or even if someone says a line from a song. The last most recent horrible song was "This Is It" by Huey Lewis and the News. I actually liked that song before it got stuck in my head for 3 days.