"It is difficult to keep the public interested," sang soprano Carmen Pelton at the Hirshhorn Museum Saturday. "The public demands new wonders piled on new wonders. Often we don't know where our next marvel is coming from. The supply of strange ideas is not endless."

This text, which puts its finger on the central problem of avant-gardism as a way of life, is from "The Show," a short story by Donald Barthelme, set to music, by Stephen Dembski and given its world premiere Saturday by the 20th Century Consort. "It's a very, very strange text," said Dembski in a preconcert symposium, and Christopher Kendall, the artistic director of the consort who commissioned the new work, agreed. In short, precisely what a text on the plight of the avant-garde should be.

The verbal brilliance of Barthelme's prose gets exactly the right treatment from Dembski - highly skilled but unobtrusive, accenting and phrasing the words but never overwhelming them, subtly pointing out the surrealistic wit and pathos in the text without trying to make points on its own or force the words into alien forms. It is music for connoisseurs, and under Kendall's direction Pelton and the consort gave it a superb performance.

In comparison, Joseph Schwanterner's "Two Poems of Agueda Pizarro" seemed rather heavy-handed, but William Doppman's "Spring Songs" were an absolute delight, superbly varied in style, rich and deep in emotional texture and ingenious in drawing a variety of effects from only four performers. Pelton's musical intelligence is as resourceful as her remarkable voice and contributed greatly to the effect of all three works.

Also on the program: Thomas Christian David's ingratiating, neoromantic Trio for violin, clarinet and piano and Mario Davidovsky's "Synchronisms No. 1" for flute and sound track, which is becoming (deservedly) a contemporary classic. Sara Stern integrated her flute splendidly with the taped sounds. Also worth mentioning are violinists Elisabeth Adkins, pianist Lambert Orkis and Loren Kitt, who played clarinet (exquisitely), recorder, harmonica, bowed cymbal and a few unidentifiable instruments.