Vocalist Norma Winstone’s nonchalant elegance and humor — and her musically adventurous backing duo — held the audience’s attention at the Cistern on Friday’s Wachovia Jazz kick-off.

The opening-night gig might not have been the swingin’ jazz concert under the oaks some audience members expected. There weren’t many elements of be-bop, lounge, or big band for foot-tappin’ or finger-snappin’. And there wasn’t any camp or cliché.

The soft-rolling set from British singer Winstone and her eclectic backing duo reflected the open-minded, all-inclusive attitude and the international vibe the series has been nurturing for years. It captured the sense of refinement and the musical sophistication Spoleto Jazz director Michael Grofsorean hopes to feature each year.

Winstone gladly shrugs off the jazz lady tag, anyway. That said, she and her bandmates — pianist Glauco Venier (from northern Italy) and woodwind man Klaus Gesing (based in Vienna) — delved into more than a few attention-grabbing moments of jazzy improvisation and tonal interaction during their unusual performance.

After a heartfelt introduction from Grofsorean, Winstone and the fellas greeted an audience of about 600 (the Cistern lawn looked about two-thirds full), and situated themselves in tight formation at the stage front. “Good evening … we’re just drying off the keys,” Winstone remarked, referring to the humidity in the air as Venier pat-dried his ivories with a towel. The weather might have been a bit still and balmy, but Winstone’s wit was colorful and dry. Her little anecdotes and remarks between songs were charming and humorous.

They opened the 90-minute set with a new arrangement of the title track from their latest album, Distances, a slow-tempo, piano-driven ballad in loose 3/4 time.

With virtuosic technique, Venier conjured some unusual sounds from his piano — occasionally reaching into his instrument to mute, pluck, or strum the actual piano strings — while Gesing bended harmonic (or sometimes dissonant) phrases over the chord progressions with his bass clarinet.

Gesing switched between his tall, thin bass clarinet to a soprano sax throughout the night, playing both with a mellow tone and wide range. His clarinet work was most impressive, either going deep in tone into gurgly bassoon territory, clicking loudly on the key pads for accents, or even sailing up into a higher register. He avoided the squawk and shriek of what some jazz cats get out of the soprano sax, too.

Winstone remained wonderfully nonchalant through the set. Her rich, breathy voice was the heart of the concert. Her more monotone, verse-heavy moments of the performance resembled a spoken-word poet with a bit of musical accompaniment more so than a front lady with a jazz band backing her up. Polished but sincere, Winstone demonstrated a range of vocal manners from song to song.

Dynamically, things eased back and forth, from mildly upbeat to glacier-like slow, from politely cheerful to morose. They introduced few new pieces from their forthcoming album Stores Yet to Tell (due in September) and touched on more than a few tracks from Distances. The moody and percussive feel of “The Mermaid” stood out as a highly syncopated set highlight.

Other bright moments included a clever and soulful reworking of John Coltrane’s “Giant Steps” (Winstone renamed it “Into Gentle Stride”), and an unexpectedly groovy version of the Fred Neil song “Everybody’s Talkin'” — a pop song made popular by the late Harry Nilsson (featured in the 1969 film Midnight Cowboy). Another stand-out was a peppery cover of American bassist/composer Steve Swallow’s “Ladies in Mercedes,” one the livelier numbers of the otherwise mellow, sparse set.

Glauco and Klaus were terrific, but one wonders what kind of full-band sound they could have produced with an additional rhythm section (drums, bass, strings). With some extra percussion, some of the music might have engaged or lured the audience more effectively (some attendees looked enthralled during the show, while others seemed fidgety and uninterested). As it was, Winstone’s tidy combo expressed itself with a gentle delivery in an airy spirit.