A piece called "Apprehension" by Shulamit Ran shared the Twentieth Century Consort's program at the Hirshhorn on Saturday with music by Richard Rodney Bennett, Schwantner and Barto'k, and established itself as an equal even in that heavy company. Ran, Israeli by birth and a dramatic philosopher by musical inclination, has produced a powerful setting of the poem Sylvia Plath wrote in the last year before her suicide. Scored for soprano, clarinet and piano, the four movements explore the subtleties of a disturbed mind contemplating death and move from passivity through anger and terror to the final loneliness.

The soprano in this performance was Lucy Shelton, who had been uncommonly busy this week with a variety of performing obligations. So suave and focused was her involvement in this music, however, that one would never guess that she had anything else on her mind. Shelton sings even the most difficult lines with consummate accuracy and apparent ease, if not with any particular subtlety, and she seemed secure here and in sympathy with both the music and the text. Clarinetist Loren Kitt and pianist Lambert Orkis are equally at home with this idiom and added their special brand of dramatic timing to the ensemble.

Schwantner's "Wild Angels of the Open Hills," on three poems by Ursula Le Guin, is not as closely tied to the text as Ran's work is. The members of this trio (soprano, flute and harp) do double duty, playing on wine glasses, triangle, tambourine, bells (bowed and struck) and wind chimes, and they all sing now and then and whisper quite often. Even if this sounds gimmicky, it isn't. Schwantner is too fine a musical craftsman to use his forces cheaply. The sounds are splendid and his musical ideas are unfailingly interesting in their own right and not merely as adjuncts to the poetry.

The concert opened with the delightful "Commedia II" by Bennett, in which nervous motion is interrupted from time to time by marvelously expressive utterances by the flute, cello and piano, and it closed with a fine reading of Barto'k's "Contrasts."