The license of the Chamber Music Society of Lincoln Center to serve up music that no other group is equipped to provide is probably its most special distinction -- though by no means the only one. Where else, for instance, does one hear a chamber music conglomerate that includes a string quartet as just one of its many adjuncts -- in this case the Emerson Quartet, which contributed mightily to last night's concert by the organization during its regular series at the Kennedy Center.

That event found the Chamber Music Society at its finest -- illustrating as convincingly as I can recall its indispensability. Everything they did was exemplary.

What other organization would have stuck its neck out and programmed a varied and sophisticated -- almost chic -- chamber music concert around the playing of jazz pianist Keith Jarrett? And in such startling juxtaposition -- first in some of the most rhythmically incisive Bach keyboard playing I have heard since the death of Glenn Gould. And then in a new work called "Sacred Ground (for the American Indian)," for flute, clarinet, cello and piano (and a profusion of percussion instruments in which the players doubled) that takes us back to the familiar Cop-Stein (Aaron Copland and Leonard Bernstein) mold in its jagged intervals and its striking combinations of sonorities.

The Bach was an arrangement for piano and clarinet (played by Richard Stoltzman) of the D major sonata, BWV 1028, for viola da gamba and harpsichord -- not in itself from the master's top drawer, but in Jarrett's vividly pointed phrasing a joy. He found a sense of mystery in this music that is rare. Much has been made over the decades about the rhythmic affinity between jazz and Baroque music, and last night one heard it for sure.

The new Jarrett piece could have been just a token effort by him. But his ear is just too good. It has that same assurance of mood that you hear in Copland. And it reminds one of the comment from Michael Tilson Thomas on one of the Copland 85th birthday broadcasts that the greatest thing about Copland is that "he has something to say." So does Jarrett.

There was also a beautiful playing of the positively orchestral Brahms G Major Sextet, Op. 36, and a smooth performance of Beethoven's Sixth Quartet, Op. 18.