Last night's all-Mozart program with the St. Paul Chamber Orchestra at the Kennedy Center concluded with the Sinfonia Concertante for violin and viola, which is, of course, Mozart's supreme contribution to the musical literature for solo strings and orchestra. The performance, with Itzhak Perlman in the violin part and Pinchas Zukerman playing the viola and conducting, was as worthy of the piece as any I can remember. And, in fact, one does not readily recall ever having heard either artist play more beautifully alone than they did together last night.

There was the opening of the slow movement. The orchestral strings began, with one of Mozart's most disconsolate refrains. Perlman picked the melody up first, almost sotto voce. Then Zukerman responded in a major key, forced to scale his unwieldy instrument way down in sound because of what had come before.

Their timings, their accents, their phrase endings seemed coordinated down to the smallest details. This was some of Mozart's noblest music played more like a chamber work than a concerto. It was such a special occasion that before the soloists could get in place to bow the audience was already on its feet, not cheering, just respectfully applauding.

Before intermission, Zukerman played two of Mozart's independent movements for violin and orchestra--an E-major adagio and that triumph of grace and wit, the C-major rondo. Zukerman was dry and understated.

It's harder for Perlman to be understated, as it would be for anyone who naturally produces such a rich sound. But in the 5th concerto that followed, with Zukerman conducting, Perlman's romanticism and Zukerman's rigor balanced out into a slightly understated passion.

These two men have been friends, and peers, since childhood. Each must be thoroughly sick of being compared with the other. So it was neat of them to erase the need for this by playing the Sinfonia Concertante in such a way that, quite simply, it sounded like both parts were played by the same person.