London's the XX, one of the most talked about bands of 2009 and one of CMJ's most prolific acts, didn't lose any steam this week. After a Tuesday showcase at New York City's Mercury Lounge that saw a line snaking around the block and a lot of disappointed fans turned away, the foursome moved on to the Delancey Thursday night.

But their biggest show was opening for School of Seven Bells at the Music Hall of Wiliamsburg Friday night following the Depreciation Guild and Phantogram. For the XX, the venue was packed to the brim with fans and enough photographers to fill a stadium event.

To shouts of "I love your hair" and simply "I love you," the band played the majority of their debut, 'xx.' The set hinged on the dynamic between guitarist Romy Madley Croft and bassist Oliver Sim, who share vocal duties, trading off sultry, heartrending lyrics. The pair has been friends since elementary school and formed the band at London's Elliot School, the alma mater of Hot Chip, Four Tet and Burial, among others.

Sim's deep, seductive voice complements Croft's airy alto, and they frequently watch and take cues from each other despite obvious familiarity with their material. Meanwhile, Baria Qureshi supports on guitar and occasionally drums, and Jamie Smith taps away on a drum machine and keyboard.

Smith also produced the album. "We worked with a lot of producers before but it ended up sounding more like them than us," Smith told the BBC in an interview earlier this year. "Eventually just decided to do it myself."

The band, which covers Aaliyah's "Hot Like Fire" on their debut, last night played a cover of Womack & Womack's "Teardrops," which was remade by the British dance act Lovestation in the late '90s and was a familiar club track for some time.

The XX were mere pre-teens then, but their clean, well-rehearsed performance last night belied their age, nodding to musical forebears who reigned before they were even born.