Neuroscientist and musician, Daniel Levitin discuses why we understand music, or why we even bother with it. He fails to be conclusive as he tries to ratify musical perception with evolutionary theory, but it is an interesting read all the same. His (and other) research has made significant headway into mapping the brain musically (using scans), but mapping the mind musically (or any other way) is still a long way off. I found the chapter titled "What makes a Musician?" a highlight. Here he looks at what exactly constitutes 'expertise'.