Arnold Schoenberg's Suite, Op. 29, is a curious work that should be heard more often not only because it is exquisitely crafted but because it takes a lot of exposure to appreciate all its dimensions.

Its strangeness begins with its instrumentation: piano, violin, viola and cello--no surprises so far--plus three clarinets, including a bass clarinet that gives the ensemble richness and depth. The music is uncompromisingly modern in its harmonies and its often jagged rhythms; it can sound postmodern 70-odd years after its composition. But it also has a curiously Viennese nostalgia, with affectionate allusions to Bach, Beethoven and traditional dance forms. It is not the sort of music you expect to hear in a free Sunday afternoon concert in the Labor Day weekend, but there is in fact a strong holiday spirit underlying its deeply serious exterior.

It was played with spirit and precision yesterday in the Lyceum in Old Town Alexandria by the forward-looking Ensemble 2100--a performance polished, as conductor Joel Lazar told the audience, by some 20 rehearsals. This was a labor of love, and the audience responded with a warmth that does not always greet Schoenberg's music.

The Schoenberg was the final, climactic work in a program otherwise devoted to the talents of Kathleen Young, principal clarinetist of the Mount Vernon Chamber Orchestra, which sponsored the concert as part of its summer chamber music series. She played impressively in three contrasting modes: with pianist Edwin Good in William Hurlstone's lyrical, witty and conservatively styled "Four Characteristic Pieces" and Alban Berg's haunting, late-romantic Four Pieces, Op. 5. She was joined by a string quartet in a smooth performance of Carl Maria von Weber's pleasant though rather predictable Introduction, Theme and Variations.