The reviewer is the music critic of The Washington Post.

Claudio Arrau, who will celebrate his 80th birthday next Feb. 6, began making headlines as a child prodigy ("the Chilean Mozart") when he was 5. After 74 years, he shows no signs of being ready to retire from a career that must already be one of the longest in the history of music.

"I'm still under the illusion that I play about a hundred concerts per season," he tells Joseph Horowitz, who informs the reader in a scrupulous footnote that Arrau actually gave 74 concerts in the 1980-81 season. His reluctance to cut down on his schedule, he explains, is "a question of giving in to age. Without reason. If I felt weaker, that would be a reason. On the contrary, I get strength from performing. But everyone wants to protect me."

Arrau has had protectors -- and needed them -- throughout his life. His father, a doctor, died when he was only a year old, and his mother began giving piano lessons to support the family. Little Claudio was reading and writing music before he could do it with words, and nearly 80 years later he is still more fluent at the piano keyboard than in conversation. He has an impractical streak that is credible only in one whose whole life has been single-mindedly devoted to art. Horowitz, his Boswell, gives details in the book's introduction with a certain relish:

"Arrau's enduring innocence is partly a legacy of his childhood eminence. He remains the least cynical, least devious of men. He does not drink or smoke. He distrusts machines; he cannot drive a car, boil an egg, or even operate a phonograph . . . He shuns parties and loses track of small talk . . . In conversation, as at the piano, he discloses emotional strife with startling frankness. He plainly embodies the nineteenth-century model of the artist as solitary, suffering hero."

Much of "Conversations with Arrau" is devoted to technical questions on such subjects as repertoire, dynamics and phrasing, hand positions, the proper speed of a trill, the techniques of piano vibrato or "bebung" and other topics of interest chiefly to musicians and music-lovers. But a fascinating personality and a life emerge from these pages of conversation and even more from the background matter periodically supplied by Horowitz.

Arrau's precocious genius was carefully nurtured. Once the full dimensions of his talent became apparent, the Chilean government awarded him a subsidy to go to Germany and study the piano. After trying two teachers and finding them unsatisfactory, he finally settled on Martin Krause, who had studied with Liszt and who became a second father to the 10-year-old prodigy with the smug but accurate prediction: "This child shall be my masterpiece."

Under Krause's care, Arrau grew rapidly as an artist and began his career, making his formal Berlin debut in 1914 when he was 11 and playing to capacity audiences and ecstatic reviews in the next few years. Then Krause died in 1918, making Arrau an orphan for a second time. The young pianist was severely affected; for several years, he brooded over the thought of giving up his career, which suffered badly from the absence of Krause's guidance and influence. But he had a family to support, not only his mother and sister but also an aunt who had come to Berlin to join the cordon of women protecting him from the world.

He did not find his third father, psychiatrist Hubert Abrahamson of Dusseldorf, until 1924, when his life had reached its low ebb. The Chilean subsidy had ended; there were fewer concert engagements in Europe, and Germany's postwar inflation brought Arrau and his family to the brink of starvation. His American debut in the 1923 season was a disaster, chiefly because of reviews that were not hostile but lukewarm ("a player of sensitive mood, subtly dynamic, a tone painter, who can charm . . . "). An unscrupulous promoter, unsatisfied with anything less than sensational reviews, left Arrau and his mother stranded in New York, penniless. They were rescued by the Baldwin company, which paid their fare back to Berlin and gave Claudio a monthly stipend "even though I had so few concerts," he recalls. "They were marvelous," he says, and one quizzically turns back to check the photo of Arrau on the dust jacket. Yes, that is a Steinway in the background, the piano at Arrau's -- but of course the incident was nearly 60 years ago, and Baldwin has had its ups and downs since then.

Arrau's path has been straight upward since he went to Dusseldorf in 1924 and spent three months under the care of Abrahamson. Within a few years, he achieved the international star status that he still enjoys (somewhat ambivalently) today, though he did not dare return to New York until 1941, when the reviews were as spectacular as they had been everywhere else ("The finest performance of Schumann's Carnaval that I have ever heard . . . "). After Time magazine finally got around to him the next year ("A small, trim-mustached man who looks like a blend of Adolphe Menjou and Anthony Eden"), the sky was obviously the limit. Abrahamson lived until 1973, by which time the 70-year-old prodigy was able to cope. His debt to psychiatry is attested not only by his success as a pianist but by an article reprinted in this book, "A Performer Looks at Psychoanalysis," which tells the reader more about his gratitude than his writing ability.

On these carefully edited conversational tapes, however, Arrau is informative and readable on his performing preferences, techniques and quirks, his attitudes toward various composers and colleagues, his drives and superstitions, even the often harrowing details of his biography and his psyche. To flesh out the book still further, Horowitz publishes interviews with other musicians who have been associated with Arrau, including Daniel Barenboim, Garrick Ohlsson and Sir Colin Davis, a critical (and very positive) survey of his recorded repertoire, the complete itinerary of his 1954-55 season to show his rather feverish level of activity at that time, and samples of the very impressive cycles of programs he was giving in the mid-'30s. In its balance of substance and readability, "Conversations With Arrau" is very nearly a model of what this sort of book ought to be.