I remember from high school reading about how bats use SONAR to see, I think in a Richard Dawkins book, and it described the really involved biological processes that go on. The signal gets sent out with various wavelengths, bounces back, the brain analyzes the different wavelengths that return, sees how long they take to return and from which direction they're coming, and all of these different inputs are analyzed instantly to create a constantly changing map of the landscape in front of the bat. It was impressive. Then Dawkins (or whoever) reminded me that this doesn't mean that bats are "smart," in the sense that we would use the word. This is all going on in the background, and the bat isn't exactly sitting down and taking a calculus test, but it's still fascinating.
The same thing that Dawkins did for me with bat SONAR, This Is Your Brain On Music did for human hearing. I had never studied in any kind of detail how the ear and brain work together to interpret signals from the outside world and morph them into what we hear as sound. It's crazy if you think about it. The only thing that our bodies have to work with is a bunch of atoms slamming against our eardrums, causing it to vibrate at differing frequencies. From this, we are able to determine the intensity of a sound, the up-down, side-side, and back-front directions, the unique timbre of different voices, pitch, etc. All from the equivalent of being a stretched-out sheet with a bunch of ping-pong balls thrown at it, only able to feel each impact, not see the path of the incoming balls. AMAZING.
Levitin discusses the possible evolutionary advantages of music (as a precursor to true speech, for example, or as a demonstration of overall fitness when combined with highly athletic and rhythmic dancing), as well as more straight-forward explanations of musical terms and how instruments utilize construction materials and string lengths/chambers to produce vastly different timbres and pitches. I'm a musical novice when it comes to technical knowledge (like the names of notes) and being able to create music, so those parts were helpful to me, although he does warn musicians to skip certain instructionary parts.
And speaking of novices, one of the points Levitin makes is that most people dramatically underestimate their own musical prowess simply because they only listen to music and don't produce it. Yet human brains are so well-attuned to musical aspects that we are remarkably talented at complex tasks like melody identification, categorization, and overtone series recognition and completion (where our brains automatically fill in the "base" frequency of notes that have had them surgically removed).
Most of us have a lifetime of listening to music, judging music, picking out genres that we like, and can instantly recognize jarring notes and unpleasant melodies or instruments, and reproduce our favorite songs with remarkable accuracy, even if we "can't sing." That is nothing to sneeze at. We're in a relatively new era of music being something that is only performed by "experts," as opposed to being a group activity in the background of many daily tasks. Everybody can make music, and enjoy it, and while this is not Levitin's main point, it's one of the aspects I really identified with, and I don't have time to get into the many issues he covers.
If you're interested in neuroscience or music, expert or not, if you can find a copy of this book, it will be worth your time.