Promising Chilean-born singer finds her voice; Claudia Acuña at The Jazz Showcase

Even a decade ago, when the Chilean-born singer Claudia Acuña was launching her recording career, she sounded like nobody else in jazz. The South American sensibility that colored everything she sang, as well as the sometimes smoldering, sometimes imploring quality of her vocals made her an emerging artist of unmistakable promise.

But now, seasoned by uncounted performances around the world and the various hard knocks that inevitably come with a career in music, Acuña has matured into one of the most searing jazz vocalists of the under-40 generation.

She proved it with practically every song she unfurled Thursday night at the Jazz Showcase, where she’s playing with an unusually empathetic band.

Focusing on repertoire from her new CD, “En Este Momento” (“At This Moment”), Acuña showed a vocal sheen and technical control one sooner associates with a classical recital than a freewheeling jazz set.

But make no mistake, the improvisational spirit of jazz — as well as the cut-to-the-essence approach of the best folkloric singers — drove this performance. Better still, by blithely ignoring distinctions among jazz, classical and ethnic music, Acuña produced unorthodox work that only she could have fashioned.

Though she floats high notes with apparent ease, Acuña’s most distinctive colors originate in the dark middle and bottom of her alto. Hers is a voice that seems to cry out at all volumes and tempos, its dramatic urgency matched by its tonal luster.

That she’s mostly singing repertory in Spanish these days only adds to the allure of the proceedings. Before certain pieces, she offered bare-bones translations of the Spanish lyrics, giving listeners just a hint of what the song was about — the left rest to the imagination.

You didn’t need to know much more about her nocturne “Tulum,” which contemplated the stars and the ocean of a Mexican locale, to sense the magic of the place. Acuña’s soaring vocal lines, gently lilting rhythms and luxuriant, throaty low notes told the rest of the story.

Astor Piazzolla’s “Vuelvo Al Sur” (“I Return to the South”) inspired the evening’s most intimate work. Accompanied by a lone guitar, Acuña sang tender, sometimes heartbreaking phrases that swayed gently to tango rhythm.

And in “El Cigarrito,” Acuña sweetly captured the whimsy of a woman daydreaming about love and when it might find her.

In this piece, and others, Acuña reminded listeners that when the best singers are at work, it isn’t just the voice that captures the ear — it’s the creative imagination behind it.