MUSIC, THE BRAIN, AND ECSTASY.<i> By Robert Jourdain</i> .<i> William Morrow: 320 pp., $25</i>

Many of us know from our own experience that music can evoke ecstasy. But it takes a rather remarkable sum of talents to account for how vibrations in the air actually do this, without leaving the lay reader behind in a cloud of phenomenological, musicological and neurophysiological dust. In “Music, the Brain, and Ecstasy,” Robert Jourdain achieves this and more with the sweet ease of a virtuoso, introducing us to the miraculous workings of our own minds with a wonderfully sure and felicitous touch.

Jourdain, who is based in Northern California, does independent research on artificial intelligence and is a musician. He is also a splendid, imaginative writer whose prose, lucid and beautifully succinct, has all the liveliness of a Mozart allegro. That’s not easy, considering the task he has set himself in this book: to give intelligent, easy-to-grasp explanations of how very complex things work and happen.

In reading it, I found myself in the presence of a kindred spirit and, while delightedly reconsidering things I have often mused upon--such as the connection of music to the emotional and spiritual realm--I also found I was learning quite a lot about processes I never even knew were occurring.

Thanks to the wondrous economy of evolution, our embryonic gills developed into the lower jaw, the larynx and the middle ear (the latter two are the organs by which we participate physically in the world of sound). But although our hearing is of quite ancient derivation (though, as Jourdain points out, far from primordial), our brain’s capacity for making sense of what we call music came as a late development and was shaped, honed and defined by our human ancestors’ struggle to survive in the wild. Jourdain shows how it is the brain, not the ear, that actually hears and, more importantly how the brain--through its role in perceiving the edges and boundaries of sounds as well as its capacity to categorize, model relationships, establish deep hierarchies of meaning and anticipate--that helps us listen to music and enjoy it.

Along the way, we meet Parasaurolophus, a hadrosaur that thrived until the great dinosaur extinction about 65 million years ago and, with a bony resonator affixed to its snout, was the world’s first instrumentalist. We encounter the inhabitants of the planet Phyxis in AD 3,721,479, trying to make sense of the sounds etched upon a gold-covered disc brought to them by the Voyager 2 spacecraft. Jourdain concludes that they will not be able to make sense of spoken language samples contained on the disc but they will be elated to discover a Bach fugue played on a piano--though Jourdain doesn’t seem to be bothered by the thought that Glenn Gould’s peculiar brand of Bach may be the only way his music is known eons hence in the far reaches of our galaxy.

Jourdain also reminds us of why we have fingerprints (for increased grip and increased sensitivity, something a sweaty-palmed pianist knows only too well) and why a bust of Beethoven sits next to our pianos and is more important in the grand scheme of things, rather than one of Tchaikovsky, Gershwin or Lennon: “because it was he who devised the deepest phrasing hierarchies ever. . . .” Actually, my bust of Beethoven resides in my study. I keep by the piano a bust of Wagner, who devised even deeper structures than Beethoven (in “Der Ring des Nibelungen”), structures that took him 30 years to develop and require a minimum of four days (or nights) for a listener to experience properly.

In one particularly imaginative foray, Jourdain spirits us to New Guinea, where listeners at a tribal musicale take torches down from the walls of their longhouse and burn the performers on their shoulders and arms in appreciation for the emotion elicited by the music. Many were the times, in my former life as a mild-mannered music critic for a major metropolitan daily, that I longed to express my “appreciation” of a performer by scorching him in the place where he sat. I should have gone to New Guinea.

There is throughout Jourdain’s book a cheerful pessimism, or tempered optimism, that is much to be admired. He’s not afraid to report on the pretty much disastrous gap that has grown up between the composers of the last half-century--with their predilections for chaos or tyranny or sometimes both--and today’s concert audiences.

The gifted American composer Stephen Albert once told me that the problem with so much modern music is that it can’t be “internalized.” Because of its density and disorderliness, people are unable to carry it around inside their minds. Without calling anybody dirty names, Jourdain shows why this is the case by exploding the old argument, used by composers who have abandoned tonality, that complexity per se is a good thing and that if only people increased their exposure to this music, they would appreciate it more. As Jourdain repeatedly points out, although the brain loves complexity, it can handle it only within a framework that allows it to model relationships through a process of anticipation and reappraisal. Simply put: It must be able to retain something in order to predict something.

At its best, music has a mimetic quality that the brain readily grasps and enhances. Our minds enjoy the challenges and rewards of being occupied by music because our brains have been conditioned throughout the course of our evolution to deal with spatial and temporal relationships. Because the intricacy and perfectibility of relationships in music is so much greater than what we encounter in mundane existence, our brains get a taste of something outside the ordinary--and thrive on it when listening to music. This is the ecstasy Jourdain writes about.

Jourdain’s explanation of musical concepts is straightforward and accurate, though in his discussion of rhythm, I wish he had settled for the word “beat” rather than “meter.” To a trained musician, the meaning of “meter” is a bit more complicated than the concept he is trying to put across. Other than that, I found nothing to argue with.

One comes away from “Music, the Brain, and Ecstasy” with the same feeling of exhilaration one gets from reading Walker Percy. In Jourdain is a writer with a similar gift for language and imagination. And there is certainly a touch of Mozart in the way Jourdain makes complexities easy to grasp and even delightful to ponder.