For more than half a century, a certain standard in the performance of Beethoven's piano music has been identified with the name of Artur Schnabel, who was born 104 years ago last Thursday and who was once told by his piano teacher, Theodor Leschetizky: "You will never be a pianist; you are a musician." Schnabel was, in fact, both; he was a composer as well as a performer, and his compositions are admired by connoisseurs,though almost unknown to the general public.

Leschetizky's quip implied a criticism of his fellow pianists, perhaps even of himself. When Schnabel began his career, late in the past century, pianists felt free to take considerable liberties with the music they ld,10 SW,-2 SK,2 played, using it as a vehicle for the expression of their own beautiful, bruised souls and the display of their extraordinary technique.

Schnabel may be most fondly remembered, in the long run, for his often-stated conviction that some music (the late piano sonatas of Beethoven, for example) is "better than it can ever be performed." By teaching and example, he established an ideal of self-discipline and dedication to the printed score that has become the standard for later generations of pianists.

As happens so often, some of the disciples went beyond their teacher. Fidelity to the text was escalated into a kind of deadpan approach that, in extreme cases, kills the spirit by strict adherence to the letter. This was no part of Schnabel's ideal; he spent his life finding ways to reconcile fidelity to the music with expression of his own personality and ideas. But the composer's intentions, as expressed in the written score, were always foremost in a Schnabel interpretation. The best of his disciples -- Leon Fleisher, for example -- have carried on this tradition.

Since the 1930s, during a period of rapid, spectacular growth in performance techniques, Schnabel's interpretations may have been surpassed by later pianists. This is certainly true in purely technical terms, where some objective judgments are possible. Schnabel was not unduly concerned about an occasional wrong note and refused to do partial retakes of a performance to eliminate such slips of the finger (an almost universal practice in studio recordings today).

Die-hard fans treasure some of his recorded mistakes as much as his moments of deep inspiration. The mistakes are a sign that he believed in spontaneity as well as careful preparation and that, despite his high standards, he did not fall into the trap of perfectionism. He had ambivalent feelings about the recording of a performance, which he called "self-destruction through preservation."

Self-destructive or not, Schnabel's recordings have certainly preserved his art. They have been made available (and have sold not spectacularly but steadily) in each newly developed recording medium of the past half-century. Now, at the dawn of digital recording, they are beginning to appear on compact discs. Some of his solo piano recordings (notably the Beethoven sonatas) are promised for later this year. But the first to be processed into the new format are the five Beethoven Piano Concertos, recorded in London between 1932 and 1935 with Sir Malcolm Sargent conducting. These have been issued on three Arabesque compact discs (numbered Z6549 to Z6551). On Z6551, there are also two short solo piano works, the popular Andante Favori and the Polonaise in C, Op. 89, which were recorded in 1938 but have not been previously issued.

This set does not really replace the one issued by EMI in the 1960s (with deluxe packaging and superb annotations) in its "Great Recordings of the Century" series. Only the First Concerto is identical in both sets. The other four in the EMI set were recorded after World War II, not long before Schnabel's death in 1951. They embody, superbly, his later thoughts on the music, and those who have the "Great Recordings" set would be well advised to keep it, perhaps supplementing it with the Arabesque set, which contains Schnabel's first recordings of these works. Being done with a single conductor in a relatively short time, it also represents a relatively unified approach to the music.

Are these the best recordings of the Beethoven piano concertos? Ultimately, each listener must answer that question personally, on grounds that are not wholly rational. Music that is "better than it can ever be performed" is also music capable of inspiring a wide variety of valid interpretations; it has more to say than can ever be expressed in any single performance. But these performances are superb and of great historic interest; they were considered definitive by most listeners (including many then-young pianists) until the dawn of the LP era after World War II.

As for the sound in the new medium, it is in no way comparable to the richness of tone and detail available in recordings being made today. But these performances have never sounded better than they do now on compact disc. The tonal quality varies somewhat in the three hours of music, recorded over a period of several years, but the new medium brings a clarity that is perhaps the quality most desirable for full enjoyment of a Schnabel performance. The musicians seem closer on CD than they did on 78s or LP.

Sometimes the clarity may seem a bit excessive; there is a rawness in the digital sound that has been masked for a half-century by the fuzziness of analog mastering and production techniques. On the CD, you can hear surface noise from the master recording -- the sound of a stylus in a groove searching out all the audio information encoded there. This has a curious psychological impact when you know you are playing a digital recording. The sound of these discs will not satisfy those who are vainly searching for perfection and a "you are there" illusion in recordings.

But for those whose interest is in the music and the interpretation, the necessary information is satisfactorily conveyed. And the presence of more abundant sonic information makes it easier to tailor the sound to your personal taste with the controls of your audio system. Though I plan to keep the EMI set, I suspect that I will play the Arabesque set more often.

Schnabel the performer was a total classicist, dedicated almost exclusively to the music of Beethoven, Mozart and Schubert. Schnabel the composer was a total modernist who cultivated the 12-tone system with great skill. Perhaps for that reason, his compositions remain almost completely unknown. He produced a significant body of work, including five string quartets, four symphonic works, a piano concerto and his best-known work, the Duodecimet -- "a small masterpiece" according to "The New Grove," which calls him "a composer of some consequence" but gives few details.

In his Sonata for solo violin, Schnabel easily justifies that description and the title of "major composer," which violinist Paul Zukofsky gives him in the thoughtful liner notes of a new recording from CP2 Records (CP2 14, available from Musical Observations, Inc, 45 W. 60 St., New York, N.Y. 10023). The unaccompanied Sonata, as played by Zukofsky, is more than 45 minutes of rhapsodic, pensive, brilliant, lyrical music, free in form and superbly varied in expression -- the work of a musician who had penetrated to the heart of classical structures and knew but was not imprisoned by Arnold Schoenberg's system. He used atonal techniques with the spirit of a traditional musician, one who knew that the primary value of this art lies in its powers to excite and enlarge the human spirit, to evoke and express our deepest feelings. Schnabel knew there may be many systems for organizing music, but at its heart all music is one thing.

Zukofsky's performance is dazzling and should, ideally, spark interest in this famous but largely unknown musician. Schnabel's Sonata for Violin and Piano, performed by Zukofsky and Ursula Oppens, can also be had from this small company (on CP2 8). The Duodecimet is available (in a performance directed by Leon Fleisher) on Audiofon 2017. For further appreciation of Schnabel as a composer, it would be helpful to have a reissue of the String Trio that was recorded by the Galimir Trio in the 1950s and has been long unavailable. And perhaps someday we may even hope to hear recordings of his String Quartets.