This is Your Brain on Music is a great introductory book on the neuroscience of music. Although I found it weighted a bit too much toward popular science for my liking, that was its stated purpose, and there was still plenty of good information in it.
Here we have an explanation of musical timing as an analogy for a moving body:
Virtually every culture and civilization considers movement to be an integral part of music making and listening. Rhythm is what we dance to, sway our bodies to, and tap our feet to… It is no coincidence that making music requires the coordinated, rhythmic use of our bodies, and that energy be transmitted from body movements to a musical instrument. (57)
‘Tempo’ refers to the pace of a musical piece—how quickly or slowly it goes by. If you tap your foot or snap your fingers in time to a piece of music, the tempo of the piece will be directly related to how fast or slow you are tapping. If a song is a living, breathing entity, you might think of the tempo as its gait—the rate at which it walks by—or its pulse—the rate at which the heart of the song is beating. The word ‘beat’ indicates the basic unit of measurement in a musical piece; this is also called the ‘tactus’. Most often, this is the natural point at which you would tap your foot or clap your hands or snap your fingers. (59)
Levitin also delves into the possible evolutionary reasons for music, noting that music seems to always go with dance, and that the concept of the expert musical performer is very recent:
When we ask about the evolutionary basis for music, it does no good to think about Britney or Bach. We have to think about what music was like around fifty thousand years ago. The instruments recovered from archeological sites can help us understand what our ancestors used to make music, and what kinds of melodies they listened to. Cave paintings, paintings on stoneware, and other pictorial artifacts can tell us something about the role that music played in daily life. We can also study contemporary societies that have been cut off from civilization as we know it, groups of people who are living in hunter-gatherer lifestyles that have remained unchanged for thousands of years. One striking find is that in every society of which we’re aware, music and dance are inseparable.
The arguments against music as an adaptation consider music only as disembodied sound, and moreover, as performed by an expert class for an audience. But it is only in the last five hundred years that music has become a spectator activity—the thought of a musical concert in which a class of “experts” performed for an appreciative audience was virtually unknown throughout our history as a species. And it has only been in the last hundred years or so that the ties between musical sound and human movement have been minimized. The embodied nature of of music, the indivisibility of movement and sound, the anthropologist John Blacking writes, characterizes music across cultures and across times. (257)
I agree. Even though we may use modern technology to exploit musical cognitive faculties for maximum effect, the idea that music/dance is a counter-evolutionary accident seems wrong to me.
You can find the website that accompanies the book at yourbrainonmusic.com.