Sometimes a song can get stuck in your mind. Become a little piece of unwanted music, that keeps looping for the rest of your day.

Neurologists claim that stuck songs are like thoughts we’re trying to suppress. The harder we try not to think about them, the more we can’t help it. The phenomenon is also known as earworms, and the ongoing ‘dim di da da dum’ causes a kind of brain itch you can’t scratch.

http://www.openculture.com/2013/03/cant_get_that_song_out_of_my_head.html