The Piano Man : BODY AND SOUL, <i> By Frank Conroy (Houghton Mifflin/Seymour Lawrence: $24.95; 450 pp.)</i>

In this novel about the rise--and rise and rise--of a young piano prodigy, Frank Conroy has many opportunities to tell us things about music. We read at some length about the natural harmonics of scales and how practical considerations compelled the adoption of a tempered scale; one in which none of the intervals except the octave is quite true.

We read about how the different brass instruments work. We read about the principles of 12-tone music and the argument of the hero, who seems to be speaking for Conroy, that it is linked to be-bop, and that conventional tonality sooner or later creeps back in. We read several pages about how Mozart’s Concerto for Two Pianos should be performed. (In a postscript, Conroy acknowledges the advice of pianist Peter Serkin.) We hear a wise old conductor explain to the young pianist, who has just scolded the musicians accompanying him, that orchestras cannot be controlled like pianos. They are, he explains in his European accent, like the “tentagles” of an octopus:

“All those tentagles wiggling around, playing like crazy, trying not to bump in. You see? Is magic. Is a miracle they play music! So we go very easy with the octopus. Big dumb beast trying hard, he shouldn’t get confused, he shouldn’t get angry. We go easy. We say nice octopus. Sometimes we say beautiful octopus. Sometimes to the audience we say this is my dear, dear friend the octopus, please clap for the octopus.”

I find that last bit interesting and charmingly put. Some of the other bits seem more commonplace. The question, though, is what are they doing here? If Conroy had written a novel, as people did 50 or 60 years ago, about a rising steel executive, I suppose that there would be chapters explaining rolling and casting and how a blast furnace works. Perhaps the hero would get into a fistfight and nearly fall into one.

Music is no doubt closer to fiction than steelmaking is. The trouble with “Body and Soul” is the way that Conroy, who wrote the splendid memoir “Stop Time” in the 1960s, uses it. The musical material is a series of didactic riffs, some good and others so-so; and the role of most of the characters is didactic, not fictional. The role of the main character--Claude Rawlings--is almost exclusively to rise; the others are there to help him, or in one or two cases to hinder him.

It is the rising, not the protagonist, that seems to interest Conroy. Apart from the musical asides, almost everything in the novel is a square in a board game. Things happen in the squares--an adolescent crush, a marriage, a love affair, a battle to save a music store, the discovery of a lost father--but their principal function is to propel Claude, move by move, from a cramped childhood to musical glory. Only one or two of the squares command going back a space or two.

“Body and Soul” begins during World War II, when the 5-year-old Claude is living in a cramped New York apartment in the shadow of the 3rd Avenue El with his mother Emma, a 300-pound, alcoholic cabdriver. There is a broken-down upright piano--Emma was once a music-hall artiste--and Claude attaches himself to it. When he is old enough to go out alone he scavenges for quarters and earns money doing errands for Al, a kindly janitor. He plucks up the nerve to visit a music store run by Weisfeld, a European refugee, who lets him have a beginning piano book on the installment plan: a quarter a month.

To his astonishment, the boy returns almost immediately, having learned the entire book. From then on, Weisfeld will treat him like a son and look after him as long as he lives; he is the first link in the chain of patrons and fortunate events that move Claude upward. Knowing everyone in the New York music world, Weisfeld gets a famous composer to let Claude practice on his Bechstein while the servants feed him Wiener schnitzels. Soon the composer dies and the piano goes to Claude, who keeps it in a basement studio at the music store.

Meanwhile, having taught Claude all he can, Weisfeld finds him three teachers, each more exalted than the previous one. The first imparts technique, the second passion, and the third, described as “maybe the best pianist alive,” teaches the boy how to transcend himself. Later he will invite Claude--now in his mid-teens--to play Mozart with him at the fictional counterpart to Tanglewood. He will stun everyone by sight reading a Beethoven piano quartet when the pianist freezes. He will get an agent, play Carnegie Hall with a famous violinist and at the book’s end, he is about to perform his prize-winning concerto with the London Symphony, and Aaron Copland is giving him good advice.

There are other bits of excellent fortune. Claude will get full scholarships to New York’s best private school and a fine small college. A hopped-up jazz musician will slip him a sheet of be-bop harmonies before falling dead in front of him at the Automat. The scene has a moment of jarring drama; a sentence promptly deadens it: “Claude understood that he had just witnessed an event of profound importance utterly off the scale of his own experience and knowledge.”

This kind of didactic note stuns any bit of life that shows itself. “Educated by the movies, he had believed that love would conquer all.” The phrase occurs in one of the author’s awkward efforts to give his hero emotional breadth. He makes him an assiduous movie-goer. “Movies,” Conroy writes in one of several other reeky passages on the subject, “were metaphors in various realities beyond his ken, and gave him the exhilarating sense of being lifted out of his own petty and narrow surroundings.”

Moviegoing is not enough to make a character out of Claude. Conroy has reached back to what the Germans call a Bildungsroman (literally, “development novel”); that is, a novel built around the growth of its hero from childhood through his entry into the great world. “Body and Soul” is all Bildung and hardly any roman ; what there is, is jerry-built.