Two different sopranos performed at the Phillips Collection yesterday. They were both named Kathie Gaus-Woollen, but the artist who recited the texts of the Dallpiccola songs so beautifully and who sang them with such involvement, could not possibly have been the same singer who, before intermission, managed to make some of Schubert's and Brahms' greatest songs sound dull.

Gaus-Woollen has attractive voice and when she draws upon its full range of possibilities, it serves both the poetry and the purely musical dimension of the song well. In the splendid and intense "Quattro Liriche di Antonio Machado" by Dallapiccola, she maintained a concentration that projected the ideas over a wide dynamic spectrum.

For some reason, however, none of this involvement was evident in either the Schubert or Brahms groups. In Schubert's "Im Fruhling," where the singer must,almost unconciously, complete the melody begun by the piano, she chose to snatch it away instead. And mush the same could be said of Schubert's "Gretchen am Spinnrade" which, in this performance, sketched a portrait of an unyieldingly bitter and angry woman, not what Schubert had in mind at all.

Pianist Terrance Gaus-Woollen, with husbandly fidelity, mirrored his wife's performance in both the best and the worst of the afternoon. His sense of Dallapiccola's crystal counterpoint was marvelous. His Brahms and Schubert were uneven and unimaginative.