The noted pianist and conductor Vladimir Ashkenazy brought the no less famous English Chamber Orchestra to the Kennedy Center's concert hall Saturday evening for a superlative session of musicmaking.

Ashkenazy conducted Mozart's G major concerto (K.453) from the key-board in accordance with 18th century practice. His playing as always was a model of control, of beautiful sound and of musical mastery. The slow movement was too slow (Mozart marked it andante, not largatto) and rather too romantic, but, aside from this, it is hard to imagine a more lucid and convincing performance, or a better balanced and lovelier accompaniment.

Fittingly enough, on the eve of the 150th anniversary of his death Franz Schubert was represented by his fifth symphony, the small one in B flat, which is a perfect jewel. Alone among his symphonies, its balance between structure and content is beyond criticism, never falling into the excesses of repetition and unmanaged melodic effusion that mar many of the longer symphonies. Again, the performance was definitive.

The concert opened with "Variations of a Theme of Frank Bridge," written in 1937 by the late Benjamin Britten as a tribute to his teacher. The work shows the ability of the strings of the orchestra, but is not particularly significant as music.

Ashkenazy is a remarkably fine musician. As a conductor, there was no question that he accomplished exactly what he desired, and that he stimulated this fine chamber orchestra to play at its best.