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In 2009, shortly before the release of the xx’s self-titled debut album, its management called the band in for a chat. It was a conversation aimed at preparing the painfully shy, strikingly young London trio for the reception that awaited its hip-yet-seemingly-uncommercial brand of understated electronic indie rock.

“They said, ‘It’s only your debut album,'” remembers singer-bassist Oliver Sim. “‘Don’t be disheartened if this record doesn’t take you to a huge place.’ ”

Three years and over 1 million worldwide record sales later, such pessimism looks profoundly misplaced.

“They got that wrong,” says Sim with a laugh, “but I’m glad they gave us the speech they did. If they had said what was to come, I may have had a little freak-out.”

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Sim’s life — and that of fellow band members, singer-guitarist Romy Madley Croft and Jamie Smith, who handles electronics and production — has been peppered with unexpected moments ever since. The surprises started off small (Smith enduring a restaurant dinner with his parents soundtracked by the album), got bigger (Rihanna sampling “Intro” for her song “Drunk on Love,” the BBC choosing the same song as the theme for its 2010 U.K. general-election coverage) and ended up positively surreal (an invite to dinner with Jay-Z and Beyoncé, after hip-hop’s power couple enjoyed the xx’s Coachella set).

The roller coaster peaked in September 2010, when the album won the Mercury Prize for British/Irish album of the year. With the eyes of the mainstream now firmly upon them, most bands would have hit the road and wrung every last sale from the album. But the xx is not most bands.

“We were told, if we did another tour, we could do very well out of it,” says Smith. “But we were pretty much at the end of our tether with being away from home.”

So instead they stopped touring, moved out of their parents’ houses and spent a year going out dancing as Smith built a reputation as a hotshot DJ and producer under the name Jamie xx, remixing everyone from Drake to Adele.

“We fell in love with dance music,” says Smith, “and that definitely had an influence on the new record.”

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The xx’s recently released sophomore album, Coexist, debuted in the No. 1 and No. 5 slots in the U.K. and U.S., respectively, achieving new chart peaks for the band. The collection duly reveals a subtle house-music influence on songs such as “Sunset” and “Swept Away.” But, as you might expect from a band with the most instantly recognizable sound of the past decade, neither that nor a bigger budget impacts too heavily on its trademark minimalism, resulting in an album that should both satisfy those who loved the debut and attract new fans.

“Having worked with Drake and Alicia Keys in massive studios, it seemed obvious that that’s not what we’re about,” says Smith. “I like [to keep] things simple, we all do.”

And keep things simple the xx did, from defiantly hushed opener “Angels” to gloriously uncluttered closing track “Our Song,” an ode to Croft and Sim’s unbreakable bond, first forged as toddlers in Putney, South West London. They formed the band in 2005, with Smith (whom they’ve “only” known since they were 11) joining in 2007; another school friend, additional guitarist Baria Qureshi, was jettisoned in 2009.

Oddly, for two so close, Croft and Sim wrote the first album separately, e-mailing ideas to each other. This time, however, they wrote in the same room, resulting in warmer, more-accessible songs, such as “Missing” and “Tides,” that suggest the xx’s rise is nowhere near over.

So a newly confident Sim dreams of “reaching people that we didn’t [reach] on the first album.” But what advice will management dispense this time around?

“Probably the polar opposite conversation,” says Sim, giggling. “Just, ‘Be afraid, be very afraid.'”

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