IN 18th-CENTURY ITALY, the opera house was hardly the place for a music-lover. In the boxes, members of the aristocracy often sat with their backs turned to the stage, eating dinner, playing cards, flirting and gossiping and working out various intrigues. Downstairs, where the tickets were cheaper (sometimes free for favored classes such as the gondoliers in Venice), there was a lot of noise and an occasional fistfight; wenches circulated among the audience selling wine and food, and the abbati, the arbiters of operatic elegance, sat implacably reading their scores and making judgments that could mean either glory or oblivion for a composer or a singer.

Opera could be even more of an ordeal for some of the singers than for the music-lovers in the audience, as Anne Rice demonstrates in her fascinating and colorful third novel. The audience tended to respond to these performances as they would to an athletic event, and a singer who aspired to something more than total indifference or volleys of rotten fruit had to perform with the kind of vigor and versatility we see today in the Olympic decathlon. Partisanship in the audience was loud, violent and unreasoning, with no significant gradations between the singers who were venerated like gods and those who were utterly despised.

The singers who made the greatest sacrifice for their art (involuntarily, as a rule, or before they were old enough to know what they were losing) were the castrati, who are the chief protagonists of Rice's novel: male singers with the power and tonal richness of a baritone operating in the pitch range of an alto or soprano. An estimated 4,000 boys were castrated in Italy for musical purposes during the 18th century, a practice begun and perpetuated largely because of a ban on the use of women singers for opera or church choruses in the papal territories-- "Children mutilated to make a choir of seraphim," Rice calls them, "their song a cry to heaven that heaven did not hear." In some of its best moments, her novel is an attempt to evoke that cry for modern readers. Except for some dim, scratchy records made in 1902-3 by Alessandro Moreschi (1858-1922), the last castrato to sing in the Sistine Choir, the voice of a castrato trained in the traditional style is a sound fortunately unavailable to modern ears.

By all accounts (which Rice has evidently researched with some care), the castrati were -- technically, if not morally -- the products of one of the more successful episodes in man's eternal effort to improve upon nature. And the price they paid for their art was explicitly, even gleefully, accepted by audiences in an age whose cruelties seem less cosmic but more wholehearted than our own. "Eviva il coltello," ("Long live the knife"), rabid partisans would shout after a particularly impressive performance by the great castrato Caffarelli.

The objects of such curious adulation (generally designated primo uomo or first man) assumed all the airs and fiery temperament associated today with prima donnas, often adding a sort of compulsion to prove their manhood through swaggering, duels and amorous adventures. Rice retails colorful anecdotes of such episodes (which abound in 18th-century sources), including a charming dialogue in which a composer complains to Caffarelli, "You don't sing what I've written" and the singer replies, "Then write what I sing."

As for amorous adventures, they supply some of the most colorful pages in Rice's book, as they did in 18th-century anecdote; the voice-preserving operation, when performed properly, left all sexual functions intact except the ability to reproduce, giving castrati a sort of sexual freedom that became available to other mortals only with the arrival of the contraceptive pill. They were greatly in demand for both homosexual and heterosexual clandestine affairs, without which Rice's book would be considerably shorter and perhaps less interesting to some readers.

When a favorite castrato singer was performing, operatic tickets became as hot as Super Bowl tickets are today, although the audience refused to pay much attention except at certain high points of the performance. The dramas in which the vocal acrobatics appeared actually deserved this kind of inattention. At the point where she introduces Caffarelli briefly into the background of her story, Rice provides a vivid description of one of his operas:

"When the curtain rose, there were ooh's and aah's from everywhere. Gilded porticoes and arches rose against an infinite backdrop of blue sky in which the stars twinkled magically. Clouds passed over the stars, and the music, rising in the sudden silence, seemed to reach the rafters. . . . Grandly dressed women and men appeared on the stage to engage in the stiff but necessary recitative that told the opera's all too familiar and utterly preposterous story. Someone was in disguise, someone else kidnapped, abused. Someone would go mad."

She goes on about gods and sea monsters and other fixtures of baroque opera, but up to this point the description fits her novel quite well. Cry to Heaven is a tale of dark family secrets, Oedipal hatred and vengeance, complex intrigues and routine violence in which someone in fact does go mad, someone dons a disguise, and the central event is someone's abduction and abuse. The abused someone is Tonio Treschi, designated heir to the glory and burden of a leading patrician family in Venice, and the abuse is the most violent possible short of murder. He is castrated because inability to reproduce will automatically take him out of the family's line of succession but, being the stuff that Venetian noblemen are made of, he turns his liability into an asset. He becomes one of the leading castrati of his generation, bides his time until the situation is right, and wreaks a long-withheld, intricately plotted and executed vengeance on his tormentor.

Some idea of the plot's flavor and complexity (much too baroque for complete summarization) may be gleaned from a confession Tonio makes near the novel's end to a Roman cardinal who is also a former lover: "I don't know what I seek, but I must tell you the one who sent men to kill me is my own father, known to everyone as my own brother."

If that sounds a bit like something in the tradition of Dumas, the impression is not entirely incorrect. But Anne Rice repeatedly raises her novel above the routine costume romances that pour out by the hundred each year, partly through the operatic background with the special thematic overtones related to the castrati and partly through careful research and expert writing. Her research is not impeccable -- for example, she has people dancing a quadrille a century before this became a common practice -- but it is generally impressive, and her ability to block out a scene with proper background, tension, overtones, dialogue and dramatic structure, often gives abiding satisfaction. Besides being a well-tangled story, Cry to Heaven is an absorbing look at a fascinating and little-known world.