Double-A prospect with XX factor

If it is Sunday, it must be Brussels. One of the hottest new arrivals of 2009 has set forth on their first European tour, only a short hop across a handful of capital cities – but it is a step up, nonetheless.

Especially since their eerie, tremulous sound is not made for supporting the vibrant likes of Florence and the Machine, with whom the xx have toured recently. Better to perform in front of an audience primed for paying close attention, singer and bassist Oliver Sim admits. "The crowd gave us a lot of attention, which we're grateful for, but the way we play, you could still hear a lot of talking. It's great now that people have heard our album and know our music a bit better."

And soon many more will appreciate their understated charms. Since the south London four-piece emerged this year, they have earned critical plaudits both for mesmeric live performances and the aforementioned album, released in August. Having all turned 20, the band that also includes singer/guitarist Romy Madley Croft, keyboardist Baria Qureshi and beat-master Jamie Smith are set for great things, though at their own stately pace, one that reflects the spectral atmosphere they conjure.

It is ironic that on their tour manager's mobile phone, backstage at a Belgian venue, both Sim and Madley Croft sound clearer than they do on record. The pair share a diffident quality, combined with quiet, underlying confidence, that makes their work so beguiling. In separate conversations, they admit their lack of volume comes from the fact that neither of them are natural show-offs who wanted to front a band. They started making music separately, even though they had known each other since they were toddlers.

"She's like a sister to me," Sim divulges. The guitarist had been teaching herself, playing along to Queens of the Stone Age and The Distillers, when she plucked up the courage to sing in front of her oldest friend. "He was really surprised," she remembers. "Then he said he'd been singing too, so we just took it from there."

Madley Croft had by then realised her voice was overpowered by the loud, distorted sound of her favourite bands, but soon found the answer to that problem. "I had been learning about minimalism at school, Philip Glass and Steve Reich, all these sparse chords that made it easier for me to sing over." So they are not fans of Cocteau Twins or Young Marble Giants, then?

"People have said we sound like those bands, but we only started to hear them once we were close to completing the album." It is a job hazard for callow artists, being compared to outfits that disbanded before they were born, but the xx also face comparisons closer to home – all the other performers that have emerged from their alma mater, Elliott School in Putney. It is an impressive roll-call that includes members of guitar pop outfit The Maccabees; nu-folkie Adem Ilhan; his former bandmate in Fridge Kieran Hebden, better known in electronica circles as Four Tet; half of youthful string section Elysian Quartet; and Herman Li, guitarist in underground rock band DragonForce; not to mention the odd member of UK garage's infamous So Solid Crew. This sprawling comprehensive school with 1,000 students ("it looks like a prison" says Sim dismissively) first came to the attention of this paper last February, when Mercury-nominated dubstep star Burial was unmasked as William Bevan.

"Real school of rock" stories appeared and the likes of Adem provided fond memories of the place. He points that a whole generation of musicians came through at one time – including Fridge, Hot Chip and Burial. "We got to use the music rooms as much as we liked – it was a real DIY attitude. Elliott was a pretty regular school with a few rough kids, but it was inspiring seeing other people having a go – you thought, if they could do it, then so can I." So when the xx emerged those same headlines were recycled.

Their predecessors were all at least ten years ahead of them, Sim explains. He talks patiently about his old school, though it is clear he has stock answers already prepared. "We honestly had no idea about Burial and Hot Chip." The xx are, though, happy to thank the school for introducing them to such a wide range of fellow pupils. "Elliot is just a standard comprehensive with an eclectic mix of people," says Madley Croft. "I'm glad I went there rather than a place with a more limited intake." And that inner-city profile is reflected in the band's tastes, that mix contemporary R&B with guitar bands. The xx have namechecked Missy Elliott on their MySpace page, and cover Aaliyah's "Hot Like Fire" and "Teardrops" by Womack & Womack, in their own shivery style, naturally. Now having tackled an R&B classic and Eighties pop-soul, on forthcoming single "Islands", they are taking on as a B-side a newer anthem that only dropped in January, from the mini-genre UK funky, Kyla's "Do You Mind?".

This is Sim's contribution, he admits. "My older sister was into that kind of music and I just nicked it from her. I can't really differentiate between music that I like and music that influences our sound, but I imagine it must seep in somewhere." Madley Croft says something very similar about Mariah Carey, who she enjoys singing along to, she says, though you would be hard pressed to believe it judging from her vocal style on record.

It might also be something they share with Burial, an artist who quickly escaped the confines of the genre from which he emerged, while Prince fans Hot Chip have themselves successfully merged dance beats with guitars.

"What I like about both Burial and Hot Chip, and I think this goes for the rest of the band, is that they sound so organic," Madley Croft says approvingly. And what about the school's music department? While the group's guitarist is self-taught, Sim learnt bass guitar at Elliott and it is where he connected with Smith and Qureshi. Adem and Hot Chip's Joe Goddard have both reminisced about free access to its facilities that allowed them and future bandmates to find their own modes of expression. "I like to say I don't know if [music teachers] did on that purpose or just left us to our own devices," Sim says. "Though I suppose we were able to work out what we wanted to do early on."

Madley Croft remembers having access to a four-track studio at school that inspired her to get hold of her own so the band could record themselves. One of her and Sim's joint inspirations were The Kills, the duo formed by Alison Mosshart and Kate Moss's beau, Jamie Hince. "It was great two people were able to do so much," Sim explains. "But I distrust backing tracks. Once they fail, you're completely screwed." So they brought in Qureshi and Smith, to help achieve Madley Croft's "organic" sound. The uncanny atmosphere of the xx on record owes much to crackles and pulses at the edge of hearing.

It is a facet they share with dubstep, of which Smith, who provides beats and samples, is something of an aficionado, though the outside noises that seep into recordings also owe much to Madley Croft's early recording technique. "I live on a road with a police station, ambulance centre and fire service, so there are sirens going by all the time. When we started, we had to record downstairs where there was a hedge to protect us, but still... one time we pressed record and something shot by wailing, so we kept it in." Also distinctive are the vocals she shares with Sim. Rather than a Marvin Gaye / Kim Weston call-and-riposte, their styles reflect solidarity, of shared experience and the strength gained from another's support.

In the main, these are traditional love songs, yet the pair wrote the album separately: one came up with a verse and the other responded with more lines or a chorus. On record, each contributor sings his or her own lines, though from the outside their input seems interchangeable.

Like the music, the process is rather tentative, with neither really understanding what the other is writing about, Madley Croft reveals. "The way we put things together is more like a collage than collaboration, though I suppose we are going through the same things, like relationships. We just never discuss the details." Sim adds, "We are the same age, so we are bound to have similar things happen to us."

It is apt that the xx are currently on a tour of European cities, given how, like dubstep and trip-hop artists, they reflect inner-city anxieties and experiences. Yet the band never forget their manners. At the back of the album's lyric booklet, where an R&B star might thank God and endless hangers-on, is printed one simple, quietly effective message: "Thank you".

The xx's single 'Islands' is out October 26 on Young Turks