"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."
-Daniel J. Levitin