Can't get that song out of your head? An endless loop? Well, cognitive theorists have proposed that this might be a case of brain itch, and certain neural circuits being tapped into. Of course, anything that stays in the mind is of great interest to advertisers and pop song shapers, so they have a keen interest in investigating such issues. It's a whole field called Consumer Psychology, and regardless of google ads and contextual advertising, anything that can make anything else seem more enticing and desirable is going to make for a better campaign.
Back to the tunes, and the music that will never die, apparently Wolfgang had his neural circuits wired up in such a way that musical patterns sought a natural completion. His kids found that, in a story I haven't come across before, they could annoy their dad by half playing tunes and scales and waiting for the great Mozart to rush off and complete the sequence by whistling, or banging out the notes on the nearest pianoforte. Sounds apocryphal, but the whole study of the brain, and its various modules, and how they interact, function independently, subconsciously, and relay information, and generally construct the phenomena we know as The Mind, is of great interest.
It's a BBC report from 3 years ago, but its as novel today as then. Scratch here