Even though divine justice ultimately prevails in William Walton's oratorio "Belshazzar's Feast," the most exciting sections extol the Babylonian king and his idols. The oratorio's pulsating, pagan praises of "strange gods," "idols" and "devils" were defiantly sung Friday night at the Kennedy Center concert hall when the Oratorio Society of Washington, augmented by the Shenandoah Conservatory Choir, began its 30th season.

Under Robert Shafer's superb direction, the 220 singers and full orchestra told the Old Testament tale of the Jews' captivity in Babylon. Guest baritone Mark Oswald momentarily stopped the story's momentum when he eerily described the handwriting on the wall that interrupts King Belshazzar's sacrilegious drinking from Jewish temple vessels. The chorus, displaying fine diction and precise intonation, conveyed the bulk of the story with a vigorous, full-bodied sound, frequently punctuated by the orchestra's excellent brass and percussion sections.

In another 20th-century choral work, Francis Poulenc's "Gloria," based on the Latin liturgical text, the chorus skillfully maneuvered its way through brisk, energetic sections as well as slow, pensive passages. Poulenc's demanding vocal leaps and dynamic extremes allowed guest soprano Marie Hadley Robinson to showcase her consummate musicianship and beautiful, focused tone.