Singing in place of the indisposed pianist Andre Watts last night in the Kennedy Center, soprano Carmen Balthrop set out before her listeners some of the most beautiful vocal sounds to be head anywhere today.

In addition, she did the unusual by including amoung her songs groups by Juan Orrego-Salas and David Dichiera, whose names are rarely seen on recital programs. Dichiera is the general manager of the Michigan Opera Theater, but judging from his four settings of Millay sonnets, he is also a composer with great sensitivity and a keen awareness of the beauties of the soprano voice.

Finest of the four in its sustained lyric appeal and illumination of the poem is his "Loving you less than life." The succeeding "I, being born a woman" has vital wit while the others are hardly less satisfying. It would probably be better if the closing "What lips my lips have kissed" repeated the final line less often

Balthrop was in radiant voice High, soft notes floated like a silvered mist in an evening in which nothing was difficult. In songs by Wolf, Strauss and Duparc, plus Handel and Mozart arias, there may have been too much that was slow and quiet, but the art and the song were very special.

Because she is so rare a singer, Balthrop owes it to herself to examine every word, note, dynamic marking and breath for their highest musical effect. She could become one of the great singers of an age that needs them. Mark Flint's playing was at times brittle, other times somewhat warmer.