WALNUT CREEK, CA— With his audacious programming, credit veteran Director Robert Geary for pushing his Volti Chamber Singers a hair beyond. While Volti is not the most accomplished of our many chamber choruses, it is arguably the most adventurous.

In their current concert set of five a capella works, the oldest one was two years old. Many a chorus (perhaps like one you’ve been in) manages four-part harmony, perhaps with keyboard accompaniment. But here there are eight-part unaccompanied harmonies, along with precarious melismas, offbeat chords and chaos, shouts and stretches of one’s range. It’s like being parachuted into a trackless jungle with just hunting knives and matches.

If there were common themes in the current concert lineup, they were composers’ greater interest in the sounds than specific texts, as well as in immersive issues of our day, whether the environment or concern about warfare abroad.

This night, among the five works came a world premiere by Mark Winges, a U.S. premiere by Zibuokle Martinaityte, a previous Volti commission from Eric Tuan, plus pieces by Trevor Weston and Pulitzer-Prize winner Caroline Shaw, who had achieved that distinction while still in graduate school. Winges and Ms. Martinaityte were both in attendance May 13 for post-concert commentary.

If you expected a concert like a stroll in the park, you got instead a rapid-fire awakening with Martinaityte’s opus “Aletheia.” Written during the onset of the Ukrainian war, this is all vocalise devoid of consonants and devoid of language, with shout-outs, falling figures and growing chaos, ever more intense, perhaps portraying the horrors of warfare. An unusual technique brings hand to mouth intermittently, like a rapidly repeated organ key. On a theme of discovery of truth, “Aletheia” proved to be a highly effective outpouring by the Lithuanian-born composer—overtly political, yet without a single incriminating word.

In his “Words Cast Shadows” world premiere, Winges mobilizes poems by Jane Hirshfield and stimulates the 16 singers by dwelling on high tones and using less comforting intervals like seconds.

In “Hermatite,” the ever-inventive Ms. Shaw played with the letters of F, E, O, bringing to mind the chemical composition of hermatite. And then out of the blue she tosses in lines out of the Columbus-contemporary composer Josquin des Pres, “A Thousand Regrets,” to voice thoughts on climate policy and an absence thereof, emerging in a muddy French that made you wish that someone had given Josquin English lessons.

In a similar environmental vein came Eric Tuan’s “In the Rain Shadow” with the excerpt “Creosote Fractal,” alluding to a plant in the Mohave said to be many millennia old.

Trevor Weston’s “Given Sound” was full of melismas and small clumps of words, showing off Volti’s well-focused soprano section. In the end however, the San Francisco-based group Volti needs to tailor its repertoire to the talents of the singers at hand, otherwise it’s just firing off ill-shaped rockets that miss the stars.

Volti’s latest set was at St. Paul’s Episcopal Church, an attractive modern structure with large parking lot nearby.

SOUNDS AND SHADOWS, a contemporary program by the chorus Volti, May 13 at St. Paul’s Episcopal Church, Walnut Creek. Repeated Mother’s Day at Kanbar PAC, San Francisco. Reachable via (415) 771-3352, or online, www.VoltiSF.org.

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