Many authors write difficult novels, but Richard Powers' are exacting. His books are beautiful headache machines crammed with dense disquisitions on, say, virtual reality or the genetic code or the history of soap. In comparison, The Time of Our Singing -- which takes its cues merely from half a century of American race relations, a millennium of musicology, and the general theory of relativity -- is a breeze, albeit a slightly cool one.
The story opens with a mesmerizing scene: the finals of a 1961 contest to discover ''America's Next Voice.'' In an auditorium at Duke University, a pair of former Juilliard students perform a 17th-century number called ''Time Stands Still.'' A 19-year-old pianist named Joey Strom, our narrator, accompanies his 20-year-old brother, Jonah, who unlooses a pure and perfect sound to take the prize. Afterward, one man emerges from the line of well-wishers to ask, with confusion and hostility: ''What exactly are you boys?''
That is the question the young Stroms address and avoid and rage at over 631 pages. The simple answer is that they, like their younger sister, are the children of David Strom (a Columbia physicist, a German Jew) and Delia Daley (a daughter of a black Philadelphia doctor), who met on the Mall in Washington in 1939 as the contralto Marian Anderson sang in the open air. Inadvisedly, they fell in love and married. Each of their three children proves to be prodigiously talented: ''Music was their lease, their deed, their eminent domain.... Singing, they were no one's outcasts.''
That shelter will collapse, but the brothers nevertheless launch a career that would be a success if each triumph weren't undermined by a slight or a snub or a threat. In its first review of Jonah's act, for instance, The New York Times writes that he's on track to become ''one of the finest Negro recitalists this country has ever produced.'' He takes such hedged praise as a shot in the gut, refusing to be ''the Sidney Poitier of opera.''
Much of the novel's wonder derives from Powers' singular treatment of race. Beyond reworking one of American literature's hoariest and most easily stereotyped themes -- the alienation of the tragic mulatto -- he makes social observations of aphoristic force: ''Juilliard's highest talent thought of themselves as color-blind, that plea bargain that high culture employs to get all charges against it dropped.'' Most engagingly, he connects the brothers' quest for self-definition with the search for artistic transcendence. Here, 400 pages in, is a vision of Jonah at work: ''[F]or a few unchanging moments onstage, backing up into the crook of the piano, he was free. He shed who he was, what he wanted, the sorry wrapper of the self.... For a while, he'd hovered above the noise of being. Then he nosedived back in.''
That vision -- ''backing into the crook of the piano'' -- is a deliberate restatement of a scene from the book's first page. The image reappears as if it were a musical trope -- the smallest example of the novel's rich symphonic logic, its grand system of harmony and melody that amounts to an abstract marvel. And yet a reliance on the abstract is the novel's limitation. At points, the characters can seem less like people than exponents of points of view. It's easy to imagine their conversations transpiring on the stripped-down stage of an existentialist play. After several hundred pages, the book's schematic orchestrations are wearying, and the author's relentless use of figures of speech that loop back to music or science surely doesn't help. In describing the brightening of a 13-year-old's expression, for instance, he arrives at a simile both tortured and abstruse: ''Her face cleared as fast as a Beethoven storm breaking on a single-chord modulation.''
What gives? A possible clue lies in Joey's insistence that whenever musicians speak of artistic bliss it is ''just to throw the uninitiated off the scent. There is no bliss; there is only control.'' Which doesn't seem precisely true. Many elements of ''The Time of Our Singing'' are a joy to behold and must have been a pleasure to dream up. It is Powers' iron regulation of voice that constrains the novel and keeps it from delivering a fully transporting sound. His huge and hugely impressive book inspires more admiration than affection.