Romy Madley Croft of The xx, still image taken from "Basic Space" music video by Anthony Dickenson

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London band The xx came out of nowhere last August with "xx," 12 tracks of minimal pop/R&B fronted by what sounded like a pair of mumbling young lovers. The blogosphere loved it right away; American mainstream media is still catching on.

The xx plays two concerts on Black Friday, one at Sonic Boom Records in Ballard (3pm, free) and another at Neumo's later that night.

With little over a month to go in 2009, "xx" stands as the sexiest and one of the year's most inventive albums, a blend of tunes that could have come out in any of the last three decades marked by deep sub-bass that reeks of the present moment in dance/club music. Add to The xx's sonic novelty the ages of the band's members—Romy Madley Croft and Oliver Sim are 20; Jamie Smith is 21—and "xx" becomes even more unlikely, the sound of a new band getting a lot right on the first try.

"xx" feels completely about sex (sexx?), but rarely deals with the subject directly. In Croft and Sim's singing, we get the Hitchcock effect where powerful stuff is made more powerful by the fact it's not actually seen.

On "Stars," a song they wrote when they were 16, Sim sings "If you want me," and Croft completes his line: "let me know." It doesn't sound like two people talking, but their interior thoughts while they eye each other on the bus. Sex is present, but in idea form, and even that's only implied. Yet, sung with a perfect combination of shyness and boldness, "Stars" sounds like it's about to erupt.

"In actual fact, Oliver and I are never addressing each other when we're singing the songs," says Croft. "Oliver is like my oldest friend, like my brother."

Croft and Sim met when they were three years old. "I don't remember the exact meeting. I think it was our parents coming to the nursery together. Our parents are friends," says Croft.

The last track on the iTunes version of "xx" is a cover of "Hot Like Fire" by American R&B singer Aaliyah, one of pop's all-time great manipulators of sexual tension. The song's about holding off for the time being. Wait, says Aaliyah, and it'll be even better. "Hot Like Fire" came out in 1997, when Croft and Sim were seven years old.

"Oliver has an older sister who would've been about 13 or whatever when that song came out, and she was always a big fan of Aaliyah and R&B," says Croft. "I think that song comes maybe from her influence."

"Hot Like Fire" was produced in a future-funk style by Timbaland, who also produced Missy Elliott's "All n My Grill," which, in a MySpace blog post, Croft said inspired part of "Stars."

Besides Portland band Gossip's Beth Ditto, Elliott and Aaliyah were probably the last female American R&B artists to write meaningfully complicated love songs, and also songs in which a woman held complete sexual power.

"The R&B and hiphop from around that era, and definitely the Timbaland/Aaliyah stuff, it feels so much...there's a whole deeper quality to it that I really love," says Croft.

"xx" is the sexiest pop music release all year—believably sexy, not fake-sexy—but in conversation, Croft laughs and avoids talking about it. "It's cool if that's what's coming across," Croft says. She stresses: "If there's a sexy vibe, it's not coming from a connection between Oliver and I."

On the phone, it seems Croft would rather talk about anything but sex. So I take a cue from "xx" and don't push it. She says it was important for her to communicate restraint on "xx."

"If you hear it, it's worth hearing. It's not just there."