Much if not most of the best music--Haydn's "Russian" Quartets, Mozart's Requiem, Beethoven's "Rasoumovsky" Quartets, Bartok's Concerto for Orchestra, almost anything by Stravinsky--was written on commission and would not exist if someone had not asked for it with the ultimate encouragement of check in hand. For 25 years the Verdehr Trio (Walter Verdehr, violin; Elsa Ludewig-Verdehr, clarinet; Silvia Roederer, piano) has been extending its limited repertoire by commissioning works from composers of every stripe and variety. They--we--have more than a hundred new works to show for it, and more are on the horizon.

The Verdehr's program Sunday afternoon at the Phillips Collection was typically diverse. Ivan Erod's recently commissioned Trio, Op. 59, draws on altered meters and displaced rhythmic figurations in the first movement, but breaks no new ground. The concluding movement playfully explores the outermost registers of all three instruments; when these atmospherics are conjoined the effect is both daft and demented, and funny the way Buster Keaton is funny.

Another commissioned work, Libby Larsen's "Slang," incorporates all manner of informal musical styles--ragtime, boogie-woogie, Tin Pan Alley, big-band riffs, and more--and runs them by quickly and unobtrusively. Before the listener acclimates to one, or even quite identifies what's happening, another has burst forth. The measure of any composition, however, is not the precept but how well the precept is realized, and by that measure "Slang" is clever entertainment worth an occasional hearing.

Ivan Kurz's "Trio Giocoso" received its world premiere. Although Walter Verdehr described it as "mystical," with tunes "floating in the past," its effect on first hearing was more mystifying than mysterious. Ludewig-Verdehr's commanding artistry on the clarinet breathed life into what seemed a sluggish composition, making it difficult to distinguish between executant and composer.

William David Brohn's "I Got Variations" is a cheerful pastiche of Gershwin's "I Got Rhythm." Two transcriptions of Fanny Mendelssohn songs beckoned conventionally, and an arrangement of a Mozart divertimento, K. 240a, charmingly refashioned old music in a new light.