Alexander Schneider has been associated with joyous music-making for years now, and in his Brandenburg Ensemble has a chamber orchestra that shares his exuberance and embodies the spirit he has always brought to his art.

They ended their Kennedy Center program yesterday with a performance of the fourth of Bach's Brandenburg Concerti that would have had the old master himself dancing. It went at a speed it has always been intended to go but rarely does because almost no group of soloists moving that fast can stay together. Flutists Susan Rotholz and Marya Martin, anchored by the virtuoso rhythmic drive of violinist Krista Bennion, flew through the music with all the solid inevitability of much slower performances, but with the excitement and power generated by their momentum.

The performance of Haydn's early C-Major Concerto for two flutes displayed a very different virtue in this group, a marvelous flexibility and the sort of chamber ensemble unity needed to give a phrase the last touch of elegant shape.

Mezzo-soprano Frederica von Stade joined them for the Scarlatti "Salve Regina" and Handel's aria "Dopo Notte" from "Ariodante." She was the perfect soloist for the occasion, an artist whose pleasure in singing shines through every phrase. She is one of the rare ones with a legato that is as integral a part of her technical repertoire as is her flexibility and accuracy. She was in splendid voice.