For starters, it was a tough job

If it’s true in show business that some acts are tough to follow, the bill at Temple Bar on Friday proved that some acts are also tough to open for.

The night started well enough for Las Rubias del Norte, a novel New York band fronted by two former choir girls who are not blonds (rubias) but who are white North Americans, which is close enough. The name simply highlights the rarity of finding a “gringo” band performing primarily Latin American music, and old standards at that. The cultural tides normally flow in reverse, with Shakira (la rubia del sur) and others internalizing English-language pop and shedding all but traces of their native Latin culture in the process.

Going against the grain gets attention. The L.A. debut of Las Rubias, singers Emily Hurst and Allyssa Lamb, was preceded by some East Coast buzz, with glowing notices in the New Yorker and the de rigueur feature on NPR. (The Village Voice named them 2005’s “Best Band With a Glockenspiel,” Hurst’s instrument.) The California tour follows the release of their touted second CD, the enjoyable “Panamericana,” which features time-honored songs from Mexico, Peru and Cuba. (The band performs again tonight at the Coffee Backstage Gallery in Altadena, www.coffeegallery.com.)

Still, only a small crowd was on hand for the 9 p.m. set by the Brooklyn-based duo and their five-piece backup band, including former Parisian Olivier Conan on the Venezuelan cuatro, a guitar. The sparse audience may have contributed to the low-key performance, which included non-Latin numbers for variety, an aria from “Carmen” and the cowboy classic “Tumbling Tumbleweeds.”

Las Rubias have harmonies as pure as Andean air. Their stage act, though, is as stiff as High Mass. Essentially, they stand there in everyday dresses, hands clasped behind their backs, emitting heavenly sounds from their mouths. Occasionally, Hurst robotically taps her glockenspiel. Lamb, the only one who speaks, also plays melodica, or wind piano, a small keyboard blown like a flute.

Yet, there is something charming in their camp simplicity, shyness and anti-glamour. It enhances the sense that their whole act is a cultural tribute; they do this because they love the music.

“I know that we don’t dance very well,” Lamb said in introducing a cumbia, “but you can.”

But then came Cava, a bawdy, boisterous and blistering singer-songwriter from East L.A. who blew the New Yorkers away. She set about showing how the natives do it, and the growing crowd didn’t have to be invited to dance.

Cava is the nickname for Claudia Gonzalez, who could be la morena del norte, with her dark skin, long black hair and indigenous features. Hard to imagine a sharper contrast with Las Rubias, considering Cava’s ethnic look, in-your-face personality and shocking lack of pudor, the Spanish word for modesty and reserve.

Cava takes the stage like a gang claims its home turf. She prowls and teases. Then, she spreads her legs wide and sits on the cajon, a crate-like percussion instrument played almost always by men.

Cava perfunctorily apologizes for the indelicate position she must assume to beat the box, leaning over with both hands between her legs, her loose, low-cut dress draped to the sides. But once she starts, the rhythms are so entrancing she seems to forget that her bosom is bouncing out and that her legs are pulsing suggestively.

Percussion may be a man’s world, but Cava doesn’t care. It’s all about the music for her too; forget convention.

Locals may know her as the former singer with Domingo Siete and the sister of Quetzal vocalist Martha Gonzalez. Now on her own, she has teamed with inventive pianist and producer Walter Miranda, half of the acclaimed Mexican rock duo Plastilina Mosh.

The unexpected collaboration has yielded a hip tropical blend with an unabashed Chicano aesthetic. It’s a shot in the arm for East L.A.’s moribund music scene.

Local favorites Los Pinguos closed the show. And by then, the lineup showed that some acts are tough to have on either side.