From Clannad to The Corrs, Irish music has been blessed - some would say cursed - with the phenomenon of the singing family. It's a tradition born out of strong family values and even stronger sibling bonds, and it thrives in rural backwaters and small towns, supported by a solid, religious upbringing. The Screaming Orphans are the newest sisters on the block, a quartet of 20something women on the verge of a commercial breakthrough. They've been signed to Warner Music, which seems determined to corner the market in Corrs-style Celtic pop. The sisters will soon be releasing their debut album under the expert eye of top producer Mike Hedges, whose impressive portfolio includes Travis and Manic Street Preachers. Looks like Warner's means business here.

The Diver sisters - Joan, Grainne, Angela and Marie Therese - grew up in the seaside resort of Bundoran, Co Donegal. Like their opposite numbers in Dundalk, the Divers' childhood was steeped in music and song; their American mother was a professional singer, and the girls began performing in public from a very early age. While the similarities with The Corrs are evident, the differences are glaring - the Diver girls don't wear their lingerie in public, and they don't wear much in the way of makeup. Indie chic seems to be the order of the day, with jeans, Tshirts and leather jackets on show. Indie also informs the music of The Screaming Orphans - giving it a grungey sheen which is completely absent from the antiseptic sound of The Corrs. It makes songs like Little Affair, Thank You and Selfish Stupid seem warmer and more inviting - you get the impression that the Diver girls really mean what they sing, while their rivals are all honeyed words without sincerity or substance. And then there's the biggest difference of all - there's no Jim.

I'm to meet two of the Donegal dynamos, Joan and Grainne, in the Dublin offices of Warner's. I've been warned that this will not be an interview, more an extended talkathon with the girls doing all the talking. They've given me just two sisters, because trying to interview all four together would be too much for a sedate old journo like me. As it turns out, Joan and Grainne are the self-confessed "mad ones" in the Diver family, and I can barely keep up with their mile-a-minute chat.

We start at the beginning, when four young sisters from Bundoran first got up on stage and started playing a mix of traditional ballads and cover versions of popular hits. "We were playing everything from Danny Boy to American Pie," says Joan. "We worked all through the summer, playing in pubs, parish halls and holiday camps. Every year we'd go to Jersey and do a stint for the tourists. We'd be going over to London to play for St Patrick's Day. I was nine when I started playing."

"We weren't pushed into it," insists Grainne. "We just absorbed the music because it was in the house all the time. Mammy was always singing, and our uncle was always singing. It just came naturally. Eventually, though, we got bored with the music. We got sick of playing Danny Boy and The Fields Of Athenry for the tourists." "But it was great experience for us," says Joan. "We learned to be entertainers, to please a crowd. We could go back and play an old age pensioners' social club, and we'd do the job."

Soon, the girls began adding their own favourites to their set, including songs by The Indigo Girls, Red Hot Chili Peppers and REM. From there, it was a short leap of faith to writing their own tunes, and it signalled a shift from cheesy venues to credible rock spots like Whelans on Wexford Street. Besides playing their own instruments - Joan plays the drums, Grainne the guitar, Angela the bass and Marie Therese the keyboards - all four Diver girls are accomplished singers, able to harmonise with the hair-raising precision of an angel choir.

IT was this four-part vocal talent which landed them a stint as Sinead O'Connor's backing singers, accompanying her on her Gospel Oak tour, and also playing the role of support act. "We were still developing at that stage," recalls Joan. "We were still caught between the acoustic folk and electric rock.

"We didn't know where we were going, so it was great to tour with Sinead, because we got to see how the professionals do it. That was a great experience for us, but no record company would touch us still." Even Warner Music, which already had Sinead O'Connor on its roster, hesitated at first. "No matter what Sinead said, they still didn't seem to pay attention," adds Grainne. "They were saying there's no market for a girl band, and they were worried because our lead singer was also the drummer. We weren't L7, we weren't The Bangles, and we weren't The Spice Girls, so the record companies didn't know what to do with us."

Eventually, Warner UK took the plunge, signing the girls to the WEA label. "The one thing we had, though, was a really good publisher, Alistair Norbury of Blue Mountain Music," says Joan. "He also does U2 and he really stuck by us. He was into developing bands, and he gave us loads of encouragement. When we were thinking of giving it all up, he kept us positive."

Not that the girls ever seriously considered quitting - music and performing are too much in their blood, and their self-belief is too strong to be swayed by record company demands. "Some of them wanted us to be like Fleetwood Mac, with two of us up front singing, and get in session musicians, but we just said `no'. And then we met Mike Hedges, and he liked what he heard, so took us out to his chateau in Northern France to work on songs. He taught us to listen to each other's playing, and not to put too much into the tunes, but to keep it clear and uncluttered."

They also learned to criticise each other's playing, which caused a bit of tension in the rehearsal room, but, as Joan says, fighting is part of the Diver dynamic. "Oh, we're constantly killing each other! We live our lives fighting. That's what makes us what we are. There's a lot of tension there, but we get on well, and people don't notice it when we're fighting. It is kind of an abnormal life, and the four of us have to concentrate fully on this career, because that's the choice we've made and we have to stick with it. But it's a weird lifestyle, you're travelling around everywhere, living in a suitcase . . . "

"I think when you're family as well, people say it must be easy for you," says Grainne. "Well, it is easy, but it's difficult too. It's not as if you can get away from each other when you have time off. We all have the same friends, but when we're away all the time, we find it harder to relate to our friends, so we end up hanging around with each other."

The Screaming Orphans have been living this nomadic life for so long now, they're well used to it. Not for them the fate of the chronically dysfunctional musical family - they like to party but they also like to keep their feet firmly on solid home ground. Having spent their youth as teenage troubadors, the Diver sisters are experienced enough to handle what the future has in store for them. It's an uncertain future, and it hinges on whether the public wants to hear more Irish-flavoured rock-pop. The girls are confident that someone out there will want to listen.

"The album really shows the variety of what we can do," says Joan. "When we have Mike, who is an incredible producer, saying he really likes our songs, that's really encouraging. This is only the beginning for us - I'm looking forward to working on the second or third album and seeing where we are by then."

The single, Little Affair, is out now on WEA.