Like skilled playwrights, the Theater Chamber Players know that well-placed levity can function not as a distraction but as a means for intensifying the seriousness of what precedes it. The group's Saturday night concert at the Kennedy Center Terrace Theater contained mostly vocal music from the 19th and 20th centuries, heavy in content and dark in mood. Yet with just two bits of absurdity from composer Ernst Toch at the end, the emotional scales almost balanced.

These Toch nuggets were necessary, arriving after a lineup that included two melancholy Brahms pieces. The Sonata in E Minor for Cello and Piano found cellist Evelyn Elsing taking the lead role in grand fashion, with unabashed passion and a large tone to match. Leon Fleisher, tentative at first, warmed to the task in the minuet movement and fugue finale. His keyboard efforts assumed a far more sinister character in support of baritone John Shirley-Quirk in the "Vier ernst Gesaenge." Theirs was a splendid partnership; Shirley-Quirk's majestic phrasing of the biblical texts and Fleisher's commanding touch earned a standing ovation.

Mezzo-soprano Patricia Green and violinist Sally McLain teamed up for Boris Blacher's "Francesca da Rimini," in which the spirit of this murder victim speaks to Dante about her desperate love for the also-slain Paolo. Green conveyed the heroine's anguish and pathos with conviction, while McLain added jittery colorations as though depicting the winds of Hades. Green had a more difficult assignment in the world premiere of Laura Schwendinger's "Songs of Heaven and Earth," based on four works by Chinese poet Ts'ai Yen. The pitches assigned made for great leaps in register and dynamics. Green did well recounting the poet's tragic life story, and the septet behind her exuberantly took to the challenges involved. Schwendinger's score has an impressive luster and transparency, even when the textures become thick. The work could benefit from less instrumental activity in spots.

Toch's delightful "Fuge aus der Geographie" and "Valse" used a speaking chorus to twisted ends. The syllables behind the words were stretched and repeated, stretched and repeated, with voices counting out the 1-2-3 tempo amid giddy party talk in "Valse." "What a dance!" was the last line offered. "What a piece!" was the implied response by the audience's applause.