It was good to hear the Oratorio Society of Washington at the Kennedy Center, for a change, yesterday. In their recent outings at the National Shrine, which has some of the worst acoustics in the city, all that's been heard from them, for all their efforts, has been an agreeable mush. tAs suspected and confirmed here, however, they still sing very well indeed.

Yesterday's program of American music featured the premiere of "The silent Kingdom," a musical fable for children by Oratorio Society conductor Robert Shafer, written to celebrate the chorus' 20th anniversary. It is a 30-minute stage piece scored for chorus, brass, narrator-baritone and boy soprano, on a tale about a king whose silence, not responsive to the cajolings of three of the finest songs in the kingdom, is finally overcome by a peasant boys's simple song.

Shafer has provided nice settings of three Elizabethan melodies and a fine fanfare. However, the work is uneven at best and precious at worst. The narration is undistinguished, the story trite and the concept forced.

Performances of Berstein's "Chichester Psalms" and Copland folksong settings were spirited and well paced, although the diction could have been clearer.