The Los Angeles-based a cappella sextet SONOS has few rules, but those it abides by are ironclad.

“We do our best to defy stereotypes,” says Jessica Freedman. “The whole approach has been to distance ourselves from kitsch,” chimes in Ben McLain. “And we don’t go ‘dow,’” adds Rachel Bearer.

Dow?

“That’s one of the words vocal groups use to emulate an instrument, like a guitar, with a made-up syllable,” Freedman explains. “We steer clear of that in arrangements.”

With a cappella vocal groups proliferating madly on college campuses and infiltrating the mainstream via TV shows like Glee, Sonos couldn’t have emerged at a more propitious time. But the three women (Freedman, Bearer and Katharine Hoye) and three men (McLain, Chris Harrison and Paul Peglar) who produce its tapestry of tones are swimming against the tide of jukebox set lists, doo-wop inflections and collegiate shtick in their quest to take a cappella music to a new, more sensual, more musically adventurous destination.

They’ve already won plaudits from such tastemakers as Chris Douridas of L.A. bellwether station KCRW-FM, who praised Sonos’ “innovative vocal arrangements” and “inspired repertoire, supremely delivered.” “Prepare to be stunned,” advised the U.K. newspaper The Guardian, while Campus Circle lauded their “unaccompanied magnificence.” Beyond admiring the group’s sonic achievements, critics also noted its “sexual tension” (L.A. tastemaker outlet The Deli Magazine) and “sex appeal” (Pasadena Weekly).

On its debut album, SonoSings, the group combines a rich, classically choral sensibility with an ultra-modern repertoire and sonic toolkit. The result is a spellbinding fusion of ancient and contemporary sounds, as songs by the likes of Radiohead (“Everything in Its Right Place”), Sara Bareilles (an a cappella veteran herself, she joins Sonos for a rendition of her “Gravity”), Fleet Foxes (“White Winter Hymnal”), Bon Iver (“Stacks”), Rufus Wainwright (“Oh What a World”), Björk (“Joga”), Imogen Heap (“Come Here Boy”) and other cutting-edge creators are transformed into mesmerizing vehicles for voices only.

The only pre-existing pop megahit in the batch is “I Want You Back,” but the group’s moody, trip-hop rendition radically re-imagines the tune – bringing out the dark, despairing lyrics that were all but negated by the Jackson 5’s bouncy, bubblegum original. With the passing of Michael Jackson, the version serves as an emotional homage.

Harrison produced and mixed the disc (with Gabriel Mann and manager Hugo Vereker, who assembled the group, provided A&R direction on the album and dreamed up the stark reworking of “I Want You Back”); he also handled several arrangements.