Haim (No 1,235)

Hometown: Los Angeles.

The lineup: Danielle Haim (vocals, lead guitar), Alana Haim (vocals, rhythm guitar, keyboards, percussion), Este Haim (vocals, bass), Dash Hutton (drums).

The background: It's the genre clash they said would never happen – mainly because it seemed too absurd. What, mix together folk and R&B? That's insane! But that's exactly what Haim, three sisters ("and one mister" – Dash Hutton on drums) from LA, have done: fused the crystal-clear vocals and wan, wafting melodies of folk and folk-rock with the beats of R&B and given the whole thing a hi-tech polish, keeping it spacious, via the studio techniques of your favourite urban producers. You don't wonder why nobody thought of it before; rather you assume nobody would have dared because it seems so unlikely. But it works, and it works well: according to our spies – and, to be fair, reams of excitable advance press – the girls have been one of the hits at this year's SXSW, their gig packed to bursting with industry types eager to erase the memory of the Pierces' failed campaign. What went wrong with those folk-rockin' sisters? Why didn't they succeed? Because they forgot to include elements of R&B.

D'oh! It sounds so obvious now. This is where inner-city clubland meets Laurel Canyon. Think Stevie Nicks produced by Dallas Austin or the Staves in a tussle with TLC. Classic rock is in their DNA – as a teenager in the 70s, their mother won an episode of The Gong Show singing a Bonnie Raitt song while their father raised them on a strict diet of Rolling Stones, Fleetwood Mac and old-school Americana – but 90s R&B is in their veins: to wind up their superannuated rocker parents, the rebellious Haims started playing Aaliyah, En Vogue or Brandy & Monica around the house. To begin with, they accommodated Mum and Dad, forming a band with them called Rockinhaim, a bit like the Partridge Family only instead of bubblegum pop they did covers of Billy Joel and Santana tunes, with the girls handling vocal and bass chores, Mama Haim on guitar and Papa Haim on drums. Eventually, their daughters got their own way and traces of R&B began to creep into their set, which increasingly comprised originals.

And now the Haims – Este, the eldest and the one with the music degree, on bass (Brainy Haim), Danielle, the 22-year-old lead guitarist who has toured with Jenny Lewis and Julian Casablancas (Rocky Haim), and Alana, the 19-year-old on rhythm guitar, keyboards and percussion (Baby Haim) – have finalised a template for their folk&B hybrid in the shape of their debut EP, Forever. It includes three tracks, and they're all good. Better Off begins with some a cappella harmonising before the beat starts, and it's not a rock beat, it's a hip-hop one – one that wouldn't shame the new OF album. "You fucked me up, what am I to do now?" they sing, like Kelis in the body of the young Judy Collins, as the trebly bass resounds. What a concoction – one that could so easily have been a cock-up. Forever is like something perky and poppy by Pebbles, or Rhythm Is a Dancer by Gloria Estefan, only sung, as we say, by folkies, and with slashing, scything guitar and a low rumble that is totally Edge of Seventeen. You have conflicting emotions: this is odd; this is great! Go Slow is a ballad with an itchy rhythm: it's folkstep, the vocals pure, even prim, only with R&B's erotic throb and heat. The sound is superb, sparse, crisp, and when the voices go spectral, there are shades of chillwave: Wilson Phillips wound down and weirded out by Washed Out. The least probable but most surefire hit of the season.

The buzz: "A trio of LA sisters who have everyone talking big game – and actually living up to these sky-high expectations" – nylonmag.com.

The truth: It may not work on paper, but Haim are going to be huge.

Most likely to: Go their own way.

Least likely to: Commit arson.

What to buy: The debut EP, Forever, is available as a free download on their website.

File next to: The Pierces, TLC, Wilson Phillips, Tegan & Sara.

Links: haimtheband.com/.

Monday's new band: Jessie Baylin.