reams that have not been exorcised by his controversial 600-page biography, "Horowitz."

"While I was writing the book," says the slim, intense, 30-year-old pianist turned author, "I would dream about incidents that are in the book. Now my dreams are about wanting to meet and become friends with him--wanting him to accept my role as his biographer."

No chance of that, considering Horowitz's intense concern for privacy and the carefully cultivated public image he has built in a career of more than half a century.

Plaskin has taken a wealth of material that used to be music-industry gossip about Horowitz, put it into print and supplied footnotes and source references. He insists he has not done this maliciously, but in order to "present a complete picture of a very complex character."

But Plaskin acknowledges that his biography is unauthorized and not at all to its subject's liking: "Horowitz has tried so hard to protect his image and has succeeded so well that this book, no matter how true and how well-intentioned, can only come as a blow," says Plaskin. (Horowitz says, through his manager, that he has not read the book and does not intend to read it.)

According to a hearsay report in the biography, Horowitz "has jokingly said there are three kinds of pianists: Jewish pianists, homosexual pianists, and bad pianists." Beyond questions of goodness or badness, Plaskin is a pianist like Horowitz, Jewish like Horowitz and homosexual. As portrayed in the book, Horowitz apparently had homosexual leanings as well. Plaskin freely discusses his own sexual orientation without making an issue of it, and he does not think that homosexuality imposes any stigma. He is sensitive only on terminology: "Don't say 'homosexual,' " he suggests, "say 'gay.' That's not a good word, either, but there isn't any really good word."

The subject crops up only on about a dozen of the book's 607 pages, usually for a matter-of-fact sentence or two. Most of the book (approximately 60 percent) is really about Horowitz's art and his career, with exhaustive documentation on his repertoire, style and technique, recordings and concert performances through the years.

In the part that deals with Horowitz's personality, Plaskin discusses many topics, other than Horowitz's sexuality, that might be considered more damaging to his public image: insecurity, nervous breakdowns; deeply troubled domestic relations with his wife, Wanda (whose father was Arturo Toscanini), and with his daughter, Sonia (whose death may have been suicide); a high-strung, hypercritical personality; inordinate interest in money; and Horowitz's tendency to cancel concerts and other commitments at the last minute.

Much of this material is also common gossip in the music industry, and much of it is well-established public knowledge--his three prolonged withdrawals from concert life, for example, and the many occasions on which he has canceled a scheduled concert, sometimes plunging an entrepreneur into dire financial straits. But Plaskin gives abundant detail and documentation of times and places.

Is it a hostile book or a muckraking book? The author denies it vigorously and sounds hurt by the suggestion: "I liked Horowitz at the beginning of the project; I like him and sympathize with him now . . . I tried hard to find people who would say something good about him . . ."

Why would Glenn Plaskin, who had never had anything published, write a book about Vladimir Horowitz? The choice is connected with Plaskin's decision not to pursue a career as a concert pianist after long years of preparation that brought him right to the brink of it: bachelor's and master's degrees from the New England Conservatory, followed by four years of studies at the Peabody Institute, leading toward a doctoral degree. He proposed Horowitz as a topic for his dissertation and says it was rejected as "not academic enough"; then he began working his way out of a career as a pianist and into one as a writer.

"I felt dead-ended as a pianist," he says. "I didn't want that life, either as a traveling performer or as a teacher. After a 12-city promotion tour for my book, I know now that I was right about not wanting to live on the road this way. What I really like is being alone in my apartment, doing research and writing."

He took the idea of his rejected dissertation and went to 14 publishers before finding one who would give him the $50,000 advance he wanted--a remarkable sum for an unpublished would-be writer. This became $65,000 before his work was finished. "One publisher told me that he had tried to have a book on Horowitz written seven times, but sooner or later all the writers gave up," Plaskin says. He began to find out why, once he began serious work on the book.

"Fortunately for me," he says, "I had no idea of the dimensions of the work. If I had had any idea, I'm not sure I would have had the nerve to do it. It was like going on a trip, and every time you think you're there, you turn a corner and you see before you another long stretch.

"When I began the book, I only knew Horowitz through his records. I had never even heard him in live concert, though I have heard him live about nine times since then. Ignorance is bliss; I didn't know what an exhaustive, difficult job it was going to be, and I was neither positively or negatively disposed toward him as a person. It was like a Polaroid picture; over a period of a couple of years, it came into focus."

Plaskin nearly gave up, too, after his first year of work, but he was kept at the job by his therapist. He gives her credit for the completion of the work, much like Rachmaninoff, whose Second Piano Concerto would not have been finished without the aid of his psychiatrist. "It was more than I could handle," he says, "teaching myself to write, getting and arranging the material, dealing with presures from my publisher and agent and financial pressures. My therapist--a wonderful woman--showed me how to break my work up into manageable parts and work toward intermediate goals."

He began by calling Horowitz, who seemed very receptive, and had several pleasant conversations with him. "But then," he recalls, "I began asking provocative questions and I told him I wanted to concentrate mostly on things that people didn't know about him, and he said, 'I'm going to write my own book,' and he began telling his friends not to talk to me."

The book is based on three years of work, including interviews with more than 600 people, who do not include Vladimir Horowitz. Quotes from the pianist are abundant in "Horowitz," but they are not statements given directly to Plaskin; they are from other people's interviews, notably a collection of 35 taped interviews granted by Horowitz to various friends and selected journalists. These tapes were originally offered to Plaskin by "a Horowitz enthusiast--no, a Horowitz obsessive" for $5,000. "These were copies of the tapes, not the originals," Plaskin says. "I turned down his offer and decided to try to track down the originals. It took two years."

He also hired a private detective to locate some essential papers and a research assistant to track down concert programs, reviews and interviews in several languages, spanning Horowitz's career. The results of all this research, carefully indexed, now occupy several filing cabinets in his apartment. "I'm keeping it all," says Plaskin.

One subject he has approached for his next biographical project is Lena Horne; he does not want to do another biography of a classical musician. "She turned me down." he says. "She wanted a black woman, and I didn't qualify. I can understand her wanting someone who would be on her own wavelength." On that basis, he thinks, Horowitz might have accepted him as a biographer, despite differences in their time and place of birth.

Now that the three-year job of researching and writing "Horowitz" is finished, Plaskin is negotiating a contract for a series of 26 videotaped interviews with classical, popular and jazz musicians, to be aired on public television in this country and commercial television in Japan.

"I think Horowitz is the only one I will never get for this series," Plaskin says.