Great songs seem as though they've always existed, that they weren't written by anyone. Figuring out why some songs and not others stick in our heads, and why we can enjoy certain songs across a lifetime, is the work not just of composers but also of psychologists and neuroscientists. Every culture has its own music, every music its own set of rules. Great songs activate deep-rooted neural networks in our brains that encode the rules and syntax of our culture's music. Through a lifetime of listening, we learn what is essentially a complex calculation of statistical probabilities (instantiated as neural firings) of what chord is likely to follow what chord and how melodies are formed.
Skillful composers play with these expectations, alternately meeting and violating them in interesting ways. In my laboratory, we've found that listening to a familiar song that you like activates the same parts of the brain as eating chocolate, having sex or taking opiates. There really is a sex, drugs and rock-and-roll part of the brain: a network of neural structures including the nucleus accumbens and the amygdala. But no one song does this for everyone, and musical taste is both variable and subjective.
To a neuroscientist, the longevity of the Beatles can be explained by the fact that their music created subtle and rewarding schematic violations of popular musical forms, causing a symphony of neural firings from the cerebellum to the prefrontal cortex, joined by a chorus of the limbic system and an ostinato from the brainstem. To a musician, each hearing showcases nuances not heard before, details of arrangement and intricacy that reveal themselves across hundreds or thousands of performances and listenings. The act we've known for all these years is still in style, guaranteed to raise a smile, one hopes for generations to come. I have to admit, it's getting better all the time.
