I used to believe that everyone had music in their head 24/7, just like me. Actually, It wasn’t so much a conscious belief as something I simply took for granted.
For some reason, about a decade ago, I went outside my own little box and thought to ask several people if they always heard music too. To my surprise, the answer was no.
All this got me thinking about awareness – about how much is going on in our heads all the time. We are probably not aware of most of it.
All this mental feedback, the constant reworking and processing of ideas must have a purpose. Think about it…. We learn in our sleep. Many wonderful eureka moments are the product of lots of cogitation unfolding in the mental background….
What drives the content of our internal world?
Last year I spent several months mulling over which colors to paint my house. Literally hundreds of colored squares with absurd names like ‘gypsy love’ and ‘sailor’s delight’ were strewn about my office. After month or so of staring at paint chips, I realized that my minds eye was turning into a kind of psychedelic kaleidoscope. The obsession du jour was crowding out the music.
Just Tuning In 
It’s a curse, isn’t it? You can be minding your own business, thinking a late Beethoven string quartet when some jerk says “Tijuana Taxi”. Suddenly, Beethoven is replaced by Herb Alpert, and there’s nothing you can do about it. Or worse, Beethoven and Alpert jockey for position, creating a hellish quodlibet; you might even come down with a severe case of Shikele Syndrome. I envy those who don’t constantly think music.
Those unwanted intruders are the worst. I have a colleague who calls them by the rather repellant name of ‘ear worms’.