Four pouty kids from South London, barely out of their teens, the xx see nothing wrong with playing Timbaland or Jam and Lewis-style R&B with an indie band's chops. Singer Romy Madley Croft sounds like she learned her heart-of-glass cool from Nineties soul starlets like Aaliyah or Mya (the U.K. version of this album adds a cover of Aaliyah's "Hot Like Fire"). When Oliver Sim sings along on "Heart Skipped a Beat," the boy-girl vocals create a hushed after-the-party mood of frustration and desire. When Croft wonders, "Could I make it better with the lights turned off?" she's not making coy chitchat — she really wants to find out, and so will anyone listening in.