IN CALLING his recent play Amadeus, Peter Shaffer knew without doubt that everyone would identify its subject as Wolfgang Amadeus Mozart. More than 30 years ago, when Norbert Brainin and his colleagues formed the Amadeus String Quartet in London, they identified themselves unmistakably as performers of Mozart's chamber music. There is no getting round the virtually unique association of Mozart's middle name with him and him alone. He was not named "Amadeus," however, and never called himself that except in fun. He was christened Johannes Chrysostomus Wolfgang Theophilus -- "Amadeus," of course, being the Latin equivalent of the Greek "Theophilus." It was only in jesting that he signed himself "Wolfgangus Amadeus Mozartus"; his scores and other serious documents were signed "Wolfgang AmadMe Mozart."

This point is made early on in Wolfgang Hildesheimer's Mozart, published in Germany five years ago and now issued in an English translation for the first time, perhaps in consequence of the success of Shaffer's play. In both works, writers who are neither musicians nor musicologists undertake to scrape away the encrustations of worshipful prettifying in order to reveal the man as he really was; the distortion of his very name is a minor example of posterity's determination to make Mozart conform to its own myths about him. Both the book and the play are provocative, and both in their ways are entertaining; both raise many questions, but it is the book that provides far more in the way of substantial answers.

Hildesheimer, a novelist and graphic artist, put in some 20 years' work, beginning with a lecture he delivered on the occasion of the Mozart bicentenary in 1956, on the study of the phenomenon he describes as not only "the greatest and most mysterious musician of all time" but also "perhaps the greatest genius in recorded human history." In common with the playwright, he is primarily concerned neither with analyzing Mozart's music nor giving us a conventional biography, but with the enigmatic personality of the man whose death, he notes, "is easier for us to imagine than his life, which, despite all the records and interpretations, is shrouded in mystery and always will be."

Because so much does remain mysterious, or at least unexplained, a great deal of what Hildesheimer has to say is sheer speculation, but that does not mean he's gone at his task on the basis of nothing more than intuition. In preparing this study, Hildesheimer apparently examined everything in print on his subject, every traceable contemporary reprt, every available painted or drawn portrait, every surviving piece of correspondence, and the scores themselves -- Mozart's own manuscripts whenever possible -- for clues, hints, explications: "The psychograph of his character can be plotted only in musical notes." In this respect Hildesheimer is so sure of himself that he can dismiss interpretations of an aria in CosMi fan tutte suggested by Alfred Einstein and Hermann Abert with the terse phrase, "they are wrong." More to the point, these and other writers are rebuked for contributing to the popular myth of the child-man, the pure, angelic vessel through which the miracle of creation was somehow made manifest.

To be sure, most writers on Mozart have glossed over or suppressed facets of his life which contradict this myth. They exaggerate his piety and his reactions to his parents' deaths. They are embarrassed by his scatological bent, as exemplified in the correspondence with cousin Basle in Augsburg; Hildesheimer points out that even Mozart's mother, who was not musical, enjoyed this sort of expression within her family, and he gives examples from her letters as well as her son's. A reminiscence by Karoline Pichler, a Viennese novelist who knew Mozart, confirms the image of him presented in Shaffer's play:

"Once I was sitting at the piano, playing 'Non piu andrai' from Figaro; Mozart . . . came up behind me, and my playing must have pleased him, for he hummed the melody with me, and beat time on my shoulders; suddenly . . . he pulled up a chair, sat down, told me to keep playing the bass, and began to improvise variations so beautifully that everyone present held his breath . . . But all at once he had had enough; he jumped up and, as he often did in his foolish moods, began to leap over tables and chairs, miaowing like a cat, and turning somersaults like an unruly boy . . . "

The "unruliness" was probably a way of letting off steam on the part of a profoundly sensitive creative genius who was quite aware of his powers and suffered frustrations and indignities all his life while watching lesser men advance. Joseph Lange, the scholar, painter and husband of the soprano Aloysia (Weber) Lange (on whom Mozart had set his own sights before she married Lange and he, Mozart, married her sister Constanze), emerges as virtually the only commentator among Mozart's contemporaries who had anything like a real understanding of his personality. Hildesheimer tells us a good deal about Lange and others in Mozart's circle, and uncovers much about their character which may be similarly at odds with popular perceptions.

While Shaffer, concerned after all with providing an evening of entertaining theater, could indulge himself in certain liberties or stretching of the facts (for example, strongly suggesting, if not actually depicting, Salieri as capable of actually doing Mozart in), Hildesheimer drives unswervingly for accuracy in the biographical details he presents, and gives us valuable asides on librettists, competitors, sources of support, and such figures as the remarkable musical gadfly Baron Gottfried van Swieten.

Count Arco, Archbishop Colloredo's chamberlain who literally kicked Mozart out of a room by way of accepting his resignation, had earlier tried to warn him, even using a respectful tone, of exactly how the fickle Viennese would treat him if he were to settle in their city. The brilliant clarinetist Anton Stadler, toward whom Mozart felt affection as well as admiration, was apparently a bit of an opportunist, interested only in what he could get out of his friend to enhance his own repertoire. The great composer Gluck, during Mozart's dreary sojourn in Paris, would arrive at rehearsals of his own works clad in his nightshirt, so that worshipful admirers could enjoy the privilege of dressing him. The far greater Haydn lives up to his reputation as a man without pettiness or jealousy, acknowledging his young friend's greatness in the most meaningful ways.

Aloysia and another of the Weber sisters, Sophie, are cited for their accurate recollections and estimates of Mozart, as recorded some 40 years after his death. As for Constanze, whose second husband, the Danish diplomat Georg Nikolaus Nissen, helped her produce a biography of Mozart, we are reminded that we really know nothing about her feelings toward him, and the question of his associates Franz Xaver Sussmayr's possibly having been the actual father of Wolfgang Amadeus Mozart Jr. (actual name Franz Xaver Mozart) is unresolved (though Hildesheimer suggests an alternative in the light of Mozart's attitude toward Constanze and Sussmayr in his last letters).

When Hildesheimer does get into discussions of the music itself there is a bit of the earnest amateur in evidence, as when he cites D minor as "my favorite key in Mozart," and writes of the Serenade Eine kleine Nachtmusik: "But even if we hear it on every street corner, its high quality is undisputed, an occasional piece from a light but happy pen." He suggests that Franz Gruber took the melody of Silent Night from the opening of Mozart's Wind Divertimento in E-flat, K. 252, and that the finale of that work "must have inspired the rondo of Beethoven's C major Piano Concerto." The first four notes of K. 252 are indeed virtually identical to those of Silent Night, but there is no further resemblance beyond that point; the final movement's theme is that of a well-known folk-song, Die Katze lasst das Mause nicht, which Beethoven used as a secondary theme in the aforementioned rondo.

But in relating the music to Mozart's feelings Hildesheimer seems to be as assured as he is in his convincing analysis of the composer's relationship with his father. There is an astonishing abundance of persuasive insight, too, in the character-analyses Hildesheimer draws from the music, and particularly in what he finds in the opera characters as they relate to Mozart himself. It was Mozart himself, he reminds us, who chose--and insisted upon -- Figaro for operatic treatment, and who invested its characters with their striking substance. The 20-page study of the characters in Don Giovanni is more than a mere tour de force of creative imagination, and the sections on the other stage works are similarly provocative, similarly original and similarly intriguing, all valuable not only for the light they shed on Mozart's personality, but for what they show us of his skill and judgment as a dramatist, based on his own exceptional understanding of human emotions. No miaowing or somersaults here.

Numerous legends are scrutinized and corrected. Did Mozart actually have a meeting with the young Beethoven? Probably not. Did Karl Ludwig Giesecke have a hand in the libretto of The Magic Flute, after all? Hildesheimer presents strong evidence that he wrote most of it and actually invented the characters of Sarastro and Pamina. There is a useful mini-biography of Giesecke (yet another librettist with an assumed name), as there are of various other figures all but unknown to the greater part of Mozart's adoring public.

The translation is marred occasionally by shaky grammar ("neither his mother's death nor his father's were decisive blows of fate . . . "), by the repeated use of "due to the fact that" for "because," and by one or two phrases less clear than they might have been (e.g., a reference to Wagner's characters "persistently accompanied by their motives"), but in general it is a fine job, preserving what one feels must be Hildesheimer's own conversational style and flavor and enthusiasm for his project, and at no point stuffy or dry. There are two separate indices, one of Mozart's works, the other of individuals' names, as well as numerous reproductions of portraits and scores.

"The reader must test not only the veracity of my study," Hildesheimer states, "but also his own willingness to put aside his preconceptions." That willingness would seem to be implicit in the very act of opening this book; whether one is actually persuaded, rather than merely intrigued and entertained, by some of Hildesheimer's conclusions is another matter, but for the facts it does contain and for its provocativeness itself the book seems a worthwhile addition to existing Mozart lore. CAPTION: Illustration, Jacket drawing of Mozart, Copyright (c) 1982 by Maurice Sendak