A lone female voice begins the chant, then the others join in, simple and pure. Just another Christmassy recording of oh-so-ethereal early music, you might think - until you get an eyeful of the singers. Ladies and gentlemen, meet The Mediaeval Baebes. They dress sexy and talk sassy, and the biographies on their official website are not so much musical as whimsical: Cylindra; "likes clementines, enveloping herself in ivy, and space travel". Nichole; "collects Ladybird fairytale books and drinks red wine". Marie; "enjoys booze and board games".) The idea of spicing up the classics is hardly new. Sultry sopranos and feline fiddlers are ten a penny these days, and even male musicians are to be found pouting and posing all over the covers of their latest recordings of Beethoven and Brahms. But plainsong and platform shoes? Is nothing sacred? "Well," says Katharine Blake, leader and founder of the Mediaeval Baebes, "there's only actually one plainsong track on our album, which is the first track. The definition of plainsong is unaccompanied unison singing in Latin. The rest of the tracks are traditional medieval folk songs, and five are modern settings of medieval poetry." "Yeah," Ruth Galloway chips in. "People just want to talk about kinky nuns. That's why they go on about plainsong."

The 12 Baebes are in Dublin to promote their first album, Salva Nos, and if these two are anything to go by, ethereal they most definitely ain't. Ruth seems to be the practical one. Her website biography describes her as "very well travelled, having been quite simply everywhere; unfortunately she lost her marbles somewhere along the way". In person she's petite and precise and describes herself as "a computer progammer who's running out of holidays. But I want to go on doing the two jobs for as long as I can." Katharine ("Kat's likes are champagne, hot chillies and midnight skinny dipping") is the musical brain behind the Baebes, but isn't much of a talker - unless it's just that she isn't overly keen on talking to The Irish Times, for which she shows undisguised distaste when her invitation to conduct the interview in a hotel bar is declined. Perched cross-legged on the bottom of a bed in a no-smoking room five minutes later, she lights up a cigarette and explains how the band began. "We all like a drink and we all like hanging out with our female friends, so it was just an excuse to do that, really - just another thing to do while we were hanging out together." Very convenient, comments The Irish Times somewhat uncharitably, that all one's friends would just happen to be possessed of suitably angelic singing voices. "Well, basically," says Ruth, "people just came along to see if they'd like it - and some people didn't come back. We were afraid Katharine would bore us to death, to be honest, with this medieval stuff. But we loved it. And the vocal standard isn't as high as solo opera singing or anything like that."

But wasn't there a story in an English newspaper that Katharine got the Baebes together by putting an advert in a magazine? "Oh, that's rubbish," she says. "Everyone in the band is either a close friend or a friend of a friend - except one person whom I met at a festival. I told her I sang medieval music and she said, `That's brilliant', and I said, `Do you want to join my band, they're called The Mediaeval Baebes' and she said `Yes'. " "I think," volunteers Ruth, "I know where that story about the advert came from. We did meet one of the girls when we were advertising for a flat-mate. That probably got mixed in somehow. Anyway, what would the advert say? `Medieval bird required; singing optional extra. Must wear see-through clothing'." And both Baebes dissolve into delighted giggles. It's hard to dislike these girls; on the other hand, it's extremely difficult to get any information out of them. Let's try another tack. Katharine is the only member of the group to have had any musical training. What sort of training, exactly? "I was sent to the Purcell School of Music when I was 14," she says. "It's a full-time school specialising in music. I've been singing all my life, and it had always been obvious that I would choose a performance-orientated career in music, so I suppose my parents sent me there for experience. I think what I got most out of it was the choir. Our choir master used the Kodaly technique, which is a method of training the inner ear, using a combination of tonic sol-fa with special hand signals." Which is basically the sort of method she uses with the Baebes, none of whom can read music. Katharine - who, in another musical life, is the lead singer with an outfit called Miranda Sex Garden - is also responsible for the arrangements on the album and, with Ruth, plays recorder on some of the tracks. "A lot of the arrangements on the album are geared towards what the group is capable of - and there isn't much instrumentation, it's basically about keeping things simple. But because it's medieval, simplicity works." It certainly worked for Virgin Records, who offered the Baebes a contract to record Salva Nos last May, when they'd been singing together for barely a year.

But who are they singing for - do they have a definite market in mind? Much earnest shaking of heads, then they answer the question simultaneously. Katharine: "It doesn't matter; we're not geared to a specific bracket." Ruth: "See, it's like people have different sections in their record collections - and we fall into the `relaxing classics' section." Katharine: "The something-a-bit-different section?" Ruth: "A wide variety of different people like it. Little girls like it . . . " Katharine: "Yeah, they want to be like us and dress in fairy-tale outfits. And mums love it. Glowing mums all round, really." And what about the classical music people - do they like it? Have they had any reaction from, say, early music specialists? "God knows what kind of review we'll get," says Ruth, with a shrug which suggests she knows exactly what kind of review to expect (See Michael Dervan's review in The Records). "Most of the press we've had hasn't really been about the music," adds Katharine. "It's just been news stories with cheesy headlines." Well, then, let's talk about the music. Early music albums tend to go for an extremely pure, almost bloodless sound, but Salva Nos has a folky raunchiness which, according to those who know about such things, is appropriate to the singing of medieval carols and canticles. Was this a deliberate artistic decision? "Well, the majority of our numbers are quite rousing, anyhow," says Ruth. "They vary from quiet songs to some which are extremely raucous indeed, like there's one in which we end up going `Weeeeeee . . . . . " "One gig we did was hilarious," Katharine volunteers. "It was a party where a lot of people must have been on E: anyway they were dancing to rave music and when we started singing they just stopped and stared. But when we started Adam Lay Ybounden, it's got this real rhythm and they all started bopping again. So that's our rave track . . . "

Hmm. Time to inquire about the pedigree of the hurdy-gurdy player, Dorothy Carter, who also plays dulcimer on the haunting instrumental, Binnorie O Binnorie, which comprises track 14 on Salva Nos. Katharine launches into an animated reminiscence about how she was playing violin and avant-garde glockenspiel in a cabaret band in Berlin. "And there was this 62-year-old lady who played the hurdy-gurdy and dulcimer. For the encore of that show everyone had to do their own thing, and I sang Salva Nos - so it was a combination of meeting Dorothy and playing these instruments and seeing the reaction that singing a medieval song had on a cabaret audience that gave me the inspiration to start the band when I went back to London. So Dorothy really inspired it. "She's a real troubadour - born in New York, educated in London, went to New Orleans and worked on the Mississippi Queen steam boat. Then she gave up music for a while and rediscovered it on these cranky old instruments." A dulcimer is an awesome instrument, notoriously difficult to play and even more difficult to tune. "Strictly speaking, hers is actually a santor," Ruth points out. "It's the Indian version, or something."

The musical discussion having taken a somewhat peculiar turn, perhaps we should address the question of image. Katharine's interest in early music didn't, presumably, begin as a commercial gimmick, but there's no denying the potent imagery involved, and it's hard to resist giving all that virgin and nun stuff a bit of a post-modernist Spice Girls spin. I mean, let's face it, which would you rather be - a nun or a Spice Girl? "I dunno," says Katharine, with an enigmatic smile. "If you were Hildegard of Bingen, it would be OK being a nun. But as far as commercialism is concerned, I've been in the music business for the last six or seven years and I've always done exactly what I wanted to do. I think you only get manipulated if you don't know what you want to do yourself. We're not setting ourselves up as feminist icons.

"Of course, if it happens inadvertently," she adds with a positively cheesy grin, " then it might not necessarily be a bad thing."

Salva Nos is available on the Virgin label.