The xx factor: a brooding sound

Several decades of music wafted and rumbled through the halls and honky-tonks of the Texas capital city last month, some of it remembered in graffiti left backstage at the nightclub La Zona Rosa. Scrawled on the dressing room walls were the names of an idiosyncratic roster of talent, from the permanently obscure to the celebrated Dixie Chicks and Ladysmith Black Mambazo. And just moments before, a young trio from London called the xx were onstage, unfurling delicate waves of brooding, seductive sound.

The afternoon xx performance ended with the crashing of a single cymbal from a mallet swung hard by singer-bassist Oliver Sim, standing tall in a black turtleneck. But backstage amid the graffiti, Sim cut a different figure, slumping in a chair as he was examined by a gray-bearded doctor in khaki shorts. “He’s pretty sick,” the doctor said, reaching into his bag. He counted “one, two ...,” then injected Sim with a dose of B12, just as singer-guitarist Romy Madley Croft looked up, her eyes widening in surprise. “Oh!”

Sim would be back on his feet in time for another show hours later, the xx’s fourth at last month’s South by Southwest Music Festival, and just one of the many welcome challenges associated with being a rock band in demand.

The trio’s dreamy songs of heartbreak and obsession have won the xx critical acclaim and a growing audience of pop music tastemakers on both sides of the Atlantic, and the use of their song “Intro” in an AT&T; commercial during the Winter Olympics opened the ears of a whole other demographic. The band’s next big stateside moment will arrive when it plays the Coachella Music and Arts Festival on Saturday, in Indio.

The three soft-spoken musicians -- Croft, Sim and keyboardist/drummer/producer Jamie Smith -- will face the desert heat the same as they do every other gig: dressed entirely in black, performing quietly innovative indie rock of hushed, emotional vocals and layers of guitar, bass and electronic beats, and surprised that anyone is listening at all.

“It was writing with no intention that a lot of people would hear it, and it was writing in a very therapeutic way,” said Croft, 20, who writes the band’s lyrics with Sim. “I was getting things out of me. A lot of it was written between the ages of 15 and 19. There were a lot of feelings going on there.”

The music on the xx’s self-titled debut album balances a passion for thoughtful, revealing lyrics with lengthy instrumental passages and dark, sumptuous grooves. On “Crystalised,” Croft duets dreamily with Sim over urgent strokes on her guitar, as they sing in harmony of glaciers, tides and desire. The sound is minimalist, and yet the voices express warmth, not distance, with electronic beats that double as driving melodies beneath the fingers of Smith. On tour, the xx beat scientist insists on performing everything live, nothing pre-programmed. And next to his collection of drum machines, a small Casio keyboard and the delay and reverb pedals, he keeps an acoustic cymbal instead of an electronic facsimile, because “it’s always slightly different every time you hit it,” Smith said with a grin.

The rough edges and spontaneous accidents are an important part of the xx sound. “If we’re all free to play completely freely, it just flows a lot better, and it means we can make mistakes,” said Smith, his tangle of curls gathered beneath a dark hoodie. “There’s a lot of mistakes on the album that I kept in ... all the sounds that creep in, little blemishes on the guitar.”

The three met as teens in Southwest London. Croft and Sim were the first to collaborate, and shared an interest in the louder roar and riffs of Queens of the Stone Age and the Distillers, before expanding their interests to include the Kills and the Pixies. They connected with Smith and keyboardist-guitarist Baria Qureshi at the Elliott School, a performing arts campus, and together created what became the xx.

They were all still 18 when approached by the indie label Young Turks after a performance and were encouraged to experiment and, eventually, record in a studio, said Croft, “the size of a large bathroom.”

The debut album’s 11 songs were recorded by the original quartet from November 2008 through April 2009, with Smith as producer. The fall release of “xx” was greeted warmly by critics but by the end of last year, the group became a trio with the exit of Qureshi.

“It was a decision that the three of us made,” said Sim of the xx members who remained. “We had been a band since we were 16, and I think we generally grew up to be very different people.” Qureshi’s departure meant the cancellation of some imminent tour dates, though the xx was quickly back to a busy schedule and commitments on the road. In London, Sim and Smith still live with their parents, and Croft lives with a stepmother and “floats around with some friends,” when the trio is home at all, which isn’t often.

At Austin’s Central Presbyterian Church, the xx were gathered in a big room of white brick and stained glass, with echoing acoustics that added an extra thud to the beats, much to Smith’s displeasure. And yet the old parish’s solemn atmosphere fit the band’s soulful, understated presence, even as Sim was back to smashing the cymbal in a startling crescendo.

Just as crucial, though, are the moments of calm and quiet, when the xx are at their most hypnotic and vulnerable. “Not all bands appreciate silence,” Croft said later. “They want people to be cheering and dancing. For us, silence really works because we feel people can hear more things.”

calendar@latimes.com