It’s five minutes till showtime in the Banqueting House at Whitehall Palace, London. The paparazzi are in place, hogging the edges of the red carpet outside. The waiters are popping champagne corks at a frenzied pace. Four hundred industry “insiders” are filling the hall with echoing chitter-chatter, and Simon Cowell’s “very special” video message is synched up and ready to roll. Up the walls, projected several metres high, are portraits of the four slinky girls we’ve been asked along to gawp at. Lips glossed, skin tanned, teeth bleached, with skirts so micro I’m panicking for their modesty on the raised stage they’re about to take, Escala are not your grandmother’s idea of a string quartet. They are 15 minutes late, then half an hour, holed up in a nearby hotel putting the final touches to their eye shadow. I suppose this is what you call “buzz”.

It’s hard to equate such aggressively tabloid glamour with the four girls I’d met the day before in a desolate rehearsal studio in Bow, east London. They’d shuffled in wearing hoodies and jeans, fiddles strapped to their backs, sleepy, polite and normal-looking. Victoria Lyon, 25, Chantal Leverton, 25, Izzy Johnston, 24, Tasya Hodges, 26, had been doing the wedding and bar mitzvah circuit together for two years, before which they were grafting at various top-drawer music schools. They’re unremarkable, middle-class gals with serious talents gleaned from practising and honing their art every day for two decades. The upside is that their sound production is exquisite. The downside is that, as pop personalities go, they were devastatingly bland. And bland doesn’t cut it with Cowell. A makeover was required.

His totty-making machine clunked into gear after the girls auditioned for ITV’s Britain’s Got Talent in May (10m viewers, can you believe?), when Cowell – one of the judges – got that sinister half-smile you know means he’s only thinking about one thing. Money! Doubtless he was also thinking of Il Divo, one of his record label’s most successful acts. If you aren’t familiar with their oeuvre, it consists of pop ballads and classic-lite sung by four greasy hunks who wouldn’t look out of place in the cabaret at Club Med. They have, unfathomably, sold 22m albums, far more than, say, Justin Timberlake. Cowell calls the act “the biggest secret in music”. Now he wants another one.

At the party, his video message starts. “Thank you for agreeing to sign to the label,” he says, in that famous home counties drawl. Given that agreeing to go on Britain’s Got Talent locks you into an iron-clad deal with Cowell if he wants you afterwards, the gratitude is misplaced. “The first time I saw you I thought you had star potential,” he says. “The next time, I knew you had star potential. Having heard the album, I don’t think you girls are going to be a success in the UK, you’re going to be a success all over the world.”

Sonny Takhar, managing director of Cowell’s Syco Music – which signed the girls for £1.5m in June – takes the stage. The label also looks after Westlife, Leona Lewis, Shayne Ward and Will Young. Safe to say, it’s not Deutsche Grammophon. Syco specialises in artists of the jejune variety, whose product you can stack high and sell cheap by the checkout at Asda. Now they’re getting into the classical game again. Well, I say classical. Escala’s forthcoming debut album has a smattering of Bach, but also the DJ/producer Robert Miles and – gulp – Led Zeppelin, in a playlist destined to offend fans of classical and rock music alike.

Takhar introduces the group, stumbling over Chantal’s name, then the lights dim, the electric violins the girls have had to ditch their beloved acoustic instruments for swell to ear-blistering volume, and a gauze curtain drops to reveal the record business’s newly minted, pseudo-highbrow faked-up, sexed-up money-making machines. Needless to say, the skirts are very short indeed.

It could, of course, have been different. It’s lunchtime in Bow the previous day and Escala and I are in the canteen, drinking coffee from paper cups. They are upbeat but knackered, having worked solidly for weeks to crunch out the album in minimum time. They talk over one another, occasionally breaking off to share private jokes. It feels like a jolly break between lessons at the Royal Academy, which, it turns out, Izzy and Chantal attended. Tasya was at Guildhall, Victoria at the Royal College. Their collected CVs are fearsome, boasting the Yehudi Menuhin School, St Paul’s Girls’, Salisbury and Wells cathedral schools and a Zagreb conservatoire. They have easy manners from childhoods spent under the focus of well-intentioned, well-to-do families – their fathers are graphic designers, lawyers and businessmen – and they are serious about their art. Sort of.

However, when they emerged from the hallowed halls of Britain’s classical establishment three years ago, work was hard to come by. With the average British orchestra member’s salary standing at £22,500 a year, the girls took work as session musicians, where the best money is had supplying token strings for pop ballads by the likes of Boyzone or George Michael. “We did them all,” shrugs Izzy, the pixie-like viola player and the most ambitious of the four. “Michael Bublé, Il Divo, Westlife, Simply Red – it was easy and it paid.” It didn’t even help that the girls were prettier than the average music graduate. Lest they be influenced by any visual, rather than audio, allure, “orchestras now make you play behind a screen for your audition,” says Tasya, a cellist of Croatian descent.

In 2006, while scratching around for gigs, the foursome were put together as a saucy female quartet for the boy band McFly’s tour. Izzy and Chantal had already suffered a brief stint in an even cringier pop quartet, Wild, and knew Victoria and Tasya from the circuit. Being on tour was a blast, they say. Izzy started dating McFly’s drummer, Harry Judd, and the others became besotted with the roar of pop-arena crowds. As the tour drew to a close, Victoria’s older brother – who had cast them for the tour – suggested he manage them as a full-time quartet, originally called Scala.

The combination of short skirts and Shostakovich proved an instant hit, and for the next two years they gigged as often as three nights a week. Banking conferences, birthdays, Christmas parties – for £100 each (plus travel) they were yours for the night. In the daytime they’d teach, and Victoria even got a job with the Royal Philharmonic Orchestra (RPO). But they soon tired of the routine. Chantal, for one, felt she hadn’t practised two hours a day for 20 years simply to spend her career being perved on by bankers and told to play more quietly by controlling mothers-of-the-bride. “I needed more,” says the violinist.

As “more” was never going to mean instant bookings at the grandest concert halls of old Europe, the girls took the only option they thought they had. Telly. It was during a chance appearance at last year’s X Factor wrap party that life took this turn. “The producers for the X Factor are the same as Britain’s Got Talent. They came up to us after we played and said, ‘Do you want to do the show?’ ” says Izzy. “We thought, why not? We didn’t have anything to lose.”

For Victoria, a flame-haired violinist who’s jokey exterior disguises a serious young woman, the decision wasn’t so straightforward. She was the youngest player in the RPO and had a lot to lose if the gamble didn’t pay off.

“I was so nervous telling the rest of the orchestra what I was doing,” she says. “I just thought they’d think less of me.”

Tasya agrees. “Classical music was our life, our job. We never imagined we’d go in for something like that.”

Nevertheless, a few months later – spurred on by financial necessity and the memory of those roaring crowds – the girls found themselves outside an audition room at the Hackney Empire in the shortest, purplest dresses they could find, ready to wow Cowell and his co-judges Piers Morgan and Amanda Holden. “We were sat next to a woman whose talent it was to bark like a dog, and a man who was practising getting in and out of a sack,” says Tasya. In the end, having added an “e” to their name after a dispute with a Belgian group already called Scala, they waltzed through the show’s heats and came fifth. It turns out that four years at the Royal Academy is no match for a dog that can do acrobatics nor a chavvy teenager dancing to a hip-hop version of Singin’ in the Rain. But Cowell says he decided to sign them after the semifinal. Endorsements – Sky Sports and a rumoured deal to be the new “legs” of Pretty Polly tights – followed, and Syco shelled out serious cash to bring in Trevor Horn (who steered the likes of the original Band Aid single in the past) to produce the album. Now a roster of international gigs is being lined up for next year, during which it is hoped Escala will net £20m. Crikey.

Naturally, the girls are delighted. They’re at that awkward stage of early fame where grannies wish them well in the street, but they have yet to see any real money – and they can’t wait. But, with the possible exception of flinty-eyed Izzy, this is not the life they imagined for themselves during the thousands of hours – and hundreds of thousands of pounds – they poured into perfecting their art. One could argue the formalised training of the classical musician is a type of manufacturing, but in pop the rules are different. Easy melodies and sex appeal are the order of the day. You get the sense that Cowell would have signed them if they’d been 10% less talented, but not if they were 10% less attractive. Do they feel they’ve been over-sexualised?

“That was obviously going to happen on a TV show,” says Chantal. Tasya is more concerned. “I hope it doesn’t get in the way of our credibility.” What’s it like working with Cowell? “He’s a smooth talker,” she laughs. “But he hasn’t done a string quartet before, so he has to listen to us a bit.”

“Anyway, we don’t wear anything worse than Girls Aloud do,” says Izzy. “It’s a reality of the industry and we know the game. It had got to the stage of, ‘Oh, great, we can make a living,’ but were we feeling rewarded? No. This country is bad for snobbery, though. You go to Asia and Vanessa-Mae is huge there, but there’s an attitude about it back home.”

“Of course some people turn their noses up,” says Tasya, “but what we’re doing isn’t actually classical music and we’re not trying to pretend it is. It’s not like we’re doing this because we couldn’t go down the classical route, because we weren’t good enough. This is a choice we’re making when we’re young to have an amazing time, and to record an album. I can’t be bothered with this snobbery about us,” she adds. “We’ve all been to the right schools.”

“I really miss the orchestra and I miss classical music,” pipes up Vicky. “I only left two months ago.” She sighs. “But you have to go with the best job.” They’re all aware that being a professional musician isn’t about noble notions of preserving the classics. It’s about getting a job. All four are from musical families – Izzy’s parents run a music school in Hertfordshire and Victoria is one of six siblings who play stringed instruments to a high level. “A classical career is not an easy life,” says Tasya. “It’s what I trained for my whole life but there was more money in being a session musician for non-classical stuff. I wish there was more support for these amazing classical musicians who do such serious work.”

What do former colleagues and teachers make of their reinvention? “In one of the orchestral sessions for our album,” says Vicky, “I was in the control room and my teacher was in the first violin section.” She cringes. “But he was so nice, so supportive.” Most of their classical buddies are jobbing along, largely happy that the girls have scored such a lucrative deal. Nor is there much group in-fighting, though Izzy and Tasya say they have the odd blazing row.

Back at Whitehall, Escala are going full pelt at a cover of Wings’ Live and Let Die. The kindest thing one can say is that it would probably sound all right in an advert. It’s that sterile, perfect, unnuanced electric sound that’s surprisingly difficult to produce but ultimately vapid. But they look hot, and the production is slick, so the record execs are beaming. The video for their recording of Karl Jenkins’s Palladio has already scored 600,000 hits on YouTube (floaty skirts, beach, windy day – you get the picture), so there’s no doubt their classic-ese has popular appeal. But you could say the same for KFC or Jim Davidson. It doesn’t make it good.

I spend some time chatting to Izzy’s mother – charming, bursting with pride – her brother Guy and his girlfriend, Carol. Carol – a sweet, slightly bookish-looking young violinist – tells me she played occasional understudy when one of the girls couldn’t make a wedding. “I couldn’t imagine doing that now,” she says. “Just look at them!” Guy, a cellist, is a former Young Musician of the Year who is about to tour Japan as a soloist. Izzy told me she is in awe of him because – on paper – he isn’t as gifted as she is but has put in so much practice he’s become world-class. What does he make of Escala? “Yeah, they’re good,” he says. “Different.”

“For any musician, it’s 10% talent, 90% hard work,” Tasya told me, and evidence of effort expended here is plentiful. Goody-bags packed with MP3 players and designer cosmetics lined up by the door, silver-tongued PRs, limousines and top-quality champagne. It’s the sort of excess a girl could lose herself in, and I can only hope they stay on the straight and narrow. Britney Spears is already tragic enough – but imagine how much more tragic her tale would be if, underneath the Pan Stik and crystals, she was a classically trained mezzo-soprano?

Will all their years of formal training be undone by reeling out pop-friendly pieces night after night, I’d asked them the day before. “There’s a lot of waiting around in this job, so we try to fit in practice when we can,” Vicky said brightly, if unconvincingly. And what will they do if it all comes to an end? “Teach,” said Izzy and Victoria. Chantal added: “We can do the serious classical stuff when we’re old, wrinkly and fat.” With that, the girls packed their fiddles and headed off into their pizzazz-filled future. I just hope they keep their practice up for the day when they’re standing behind the screen auditioning for an orchestra once again, back in the land where teeth and tans don’t cut it.

Escala’s eponymous debut album is released on November 3

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