WOLFGANG Amadeus Mozart is history's most famous child prodigy. A virtuoso clavierist and a more than competent organist and violinist as well, he was equally boggling as performer, improviser, and composer. He fashioned his first minuets at the age of six, his first symphony approaching nine, his first oratorio at eleven, and his first opera at twelve.

That Mozart is also the alter ego of senior music concentrator Robert Levin is no accident. Levin dates the loss of his musical virginity at the age of five and has been busily at work ever since. In the vocabulary of a prominent member of the Music Department, he has all the "equipment": perfect pitch, near-total recall, ability to read scores at sight, digital dexterity, and a catholic if necessarily incomplete cerebral storehouse of music from the 17th century to the present. At Harvard he has been chiefly occupied as classical music guru at WHRB, in addition to somewhat less frequent exposure as pianist and composer.

Saturday night Levin did his thing(s) before a full house at Sanders Theatre. The program, entiled "Works of W. A. Mozart," included the orchestral March in D, K. 335/1 (delightful in its naivete and ludicrous use of col legno), the Sonata for Violin and Piano in B flat, K. 454, and the magnificent Piano Concerto No. 25 in C, K. 503. Levin served as pianist and was joined at appropriate moments by violinist Rose Mary Harbison and an excellent pick-up orchestra conducted by John Harbison. By and large the performances were clean, tasteful and controlled, with occasional brilliance and finesse that engendered real moments of excitement.

But the concert's primary sources of drawing power, pace Mozart, were the two previously unfinished "torsos" which Levin had brought to completion as the bulk of his thesis project. It was a product, the program stated, "of some 18 months' work in the U.S. and Europe." The first of these torsos, announced as Concerto Movement for Piano, Violin and Orchestra, K. 315f, was the more substantial of the two and received by far the better performance. To Levin's great credit, there was no noticeable break between the exposition as completed by Mozart and his own continuation based on his knowledge of and empathy with the master's style. Mozart's most essential and yet most elusive quality is balance, the result of his unique musical genius. Though it can be emulated, it can never be reproduced. Notwithstanding certain lapses of taste--e.g., a modicum of Beethovenian bravura at the conclusion of the cadenza--and lack of classical proportion, the prodigiousness of the feat was unquestionable.

LEVIN has similar success with the Quintet Movement for Clarinet and Strings in B flat, K. 516c, where Mozart had left him even more to go on. Its presentation was unfortunately marred by poor intonation and general timidity on the part of the performers, principally the upper strings.

In the case of any concert, there are always nits to pick. Mrs. Harbison and even Levin himself exhibited a tendency to rush and blur the details in more rapid passages. In addition, they both had the annoying habit of building to a climax but somehow giving up or losing concentration before the crucial moment. The result was a large number of fractured phrases and a general sense of frustration. Mrs. Harbison's intonation, like that of the quintet, was frequently poor.

Complaint, however, is bootless and beside the point. To say that the concert was enjoyable would be an understatement--it was stupendous. After all, with Levin's gifts as a pianist and composer and with Mozart as collaborator, how could anyone miss?

Whatever his ultimate commencement status, Saturday night marked the peak of Levin's undergraduate career: the fruition of a long love affair with Mozart's music accorded a spontaneous standing ovation by the audience. And that is something very few soloists beside the Archbishop of Canterbury can count as part of their memories of Cambridge. One only hopes that circumstances do not abort Levin's promise even earlier than that they did that of Mozart.