A perhaps applicable note is found in:

Why God Won't Go Away: Brain Science & the Biology of Belief, Andrew Newberg, M.D., Eugene D'Aquili, M.D., PhD., and Vince Rause, Ballantine Books, ISBN 0-345-44033-1.

In their chapter 5, these authors present their theories on how "rituals" are processed in the brain, how they affect other brain processes, and how they affect how we feel about ourselves (and those around us). My reading of what they mean by ritual (not necessarily something religious) is repetition of familiar, and almost always rhythmic, words, sounds, and/or actions. Like chanting a mantra - although not necessarily with religious intent or meaning.

"...Research reveals that repetitive rhythmic stimulation ... can drive the limbic and autonomic systems, which may eventually alter some very fundamental aspects of the way the brain thinks, feels, and interprets reality. These rhythms can dramatically affect the brain's neurological ability to define the limits of the self. The stimulation of autonomic and limbic responses ... is the force that ... (calls persons) ... to rise out of themselves and into a larger and more exhilarating state of being."

My own observation has been that when a song gets "stuck," it is usually when I am in a mood or in a situation where a change would be welcome - even if it may not be apparent at the time. Perhaps the fixation on a "stuck" song happens because "ritual" makes us feel better when we need it.

I can't present it as a good hyposthesis, but it seems like what I need to get "unstuck" is a change in my own attitude (that being much simpler, usually, than an immediate change in an external situation).

Re the book: It is written in lay (non-scientific) language; but it appears to offer credible evidences, thus not falling in the pop-science category(?). It is distinctively UN-religious in tone - I haven't figured out if these guys believe or disbelieve anything of common theological constructs. I am reserving judgment on whether to recommend it to friends, pending completion of a little more of it. (It was on sale, and curiosity stimulates unstuckedness.)

BTW, when I went back to see who had posted while I was composing this POS, I noted a related(?) thread.

John