Of today's major pianists, Peter Serkin is the one who most consistently seeks not only to move audiences but also to challenge them. The program he played at the Kennedy Center Terrace Theater Saturday was nothing if not a challenge for listeners and players as well. One is impressed just at the enormous effort involved in mastering a work such as the strenuous and severe Violin Sonata of Stefan Wolpe,a composition that never will be a crowd-pleaser but deserves to be known. Serkin and violinist Ida Kavafian performed it spectacularly.

The concert was half compositions by the late German American composer Wolpe, whose work is little known, and half by Stravinsky, whose two piano works--performed here by Serkin and the brilliant Cecile Licad--are little better known than the Wolpe. Just to hear the Stravinsky Concerto for Two Pianos and Sonata for Two Pianos done by such superb players is a rare event.

The Stravinsky Concerto is the grander of these works. It contains many of the relentlessly motoric rhythms, combined with tonal and harmonic complexities, that would reach a compositional apex later in works such as the Symphony in Three Movements. The music is classic in conception and overwhelmingly contemporary in effect.

Ending as it does in a huge fugue, one was reminded of a superficial resemblance to the finale of Brahms' mighty "Variations and Fugue on a Theme by Handel," especially in sorority--yet the Stravinsky is a "cooler" piece than the Brahms. And in its way it is just as engrossing a work.

By comparison, the Stravinsky Sonata is slighter and simpler, less than half as long as the Concerto. It is charming and elegant in the composer's typical mid-1940s style.

In both pieces, Serkin and Licad combined suavity with force, neither overwhelming the other. The works can be very difficult, as the cross-rhythms, for instance, get trickier and trickier. One doubts that either composition has often had such care and virtuosity placed on it.

Wolpe's music never has had a wide audience, and it was bold to play two of his works on one program. The Violin Sonata, from 1949, is difficult to play and to follow. It comes from a period when Wolpe was wrestling with the self-acknowledged problem that the atonal idiom was running into expressive brick walls. His material is rigorous and the solutions are enormously complex. The range of sound and ideas in these four movements are tremendous, all the way from the thickest density to being right on the brink of tonality for some measures near the end.

There was also an earlier Wolpe Oboe Sonata, which was rooted in Wolpe's fascination with folk music. It sounded a little like a more-cryptic Bartok--intense, concentrated and uptight. Rudolph Vrbsky, the National Symphony first oboe and Serkin's brother-in-law, was the player, and he was very fine. Serkin's performance of the difficult piano part was remarkable.

The Kennedy Center deserves much credit for presenting so provocative a concert.