It's rather interesting to see how different people listen to music, especially at Phish shows. Some are dancing madly, others swaying back and forth with their eyes closed, and some (like the esteemed Dr. Pauly) are playing air guitar note for note with Trey. I'm usually in this camp as well, either playing air drums or doing some kind of melody with my fingers. Based on a new study we now know that Dr. Pauly's amygdala's is shooting off sparks when he enters air guitar mode. It's a pretty interesting little article (via @robmitchum) here regarding the perception of spontaneity with regard to music. The article also includes a test to see how your ears fare. From the article:
The pianist's languid solo entwines itself with the smoke and the muffled laughter from the bar. Like a shadow, the musician's fingers glide effortlessly across the keys, and he has no sheet music in front of him. Has he memorized the piece, or is he making it up as he goes along? It’s almost impossible to tell, but if you're a jazz musician and can imagine yourself playing the music, your brain’s emotional centers might help you answer this question, a new study suggests.
All the listeners said that to make a judgment, they had to imagine themselves playing the piece in order to predict what would come next. They also paid particular attention to variations in loudness and speed. Brain scans backed this up: They showed that the amygdala—the center of the brain involved in emotion—became active as the listeners tried to put themselves in the player’s shoes. If a musician thought a piece of music was improvised, he activated the same brain networks that he would if they were improvising it themselves, including some motor centers that would let them physically play it.