It started in a garden shed in Surrey - now thousands of ordinary women are on course to become a nationwide phenomenon.
An extraordinary thing has happened in the music industry. An album released by a bunch of nobodies - 987 nobodies, to be precise - has entered the charts.
This is Rock Choir: the massed voices of housewives, supermarket check-out girls, grannies, students... anyone who wants to sing - even if they're tone-deaf.
Together they belt out the soundtrack of our lives - pop, gospel and Motown hits going back to the 1960s, kicking off with a finger-snapping version of You Can't Hurry Love.
Talking about the phenomenon on his Radio 2 show, Chris Evans said, 'Music industry records are set to be smashed.'
Pundits everywhere are scratching their heads and asking, 'What is Rock Choir? And how have these nobodies pulled it off?'
The woman behind it all laughs her husky laugh and says, 'People think we're some big, glamorous operation, but there are just four of us organising everything from my garden shed in Farnham, Surrey. I'm not driving a Porsche or anything.'
Perhaps she should be. Thanks to the vision, charisma and sheer hard slog of 36-year-old Caroline Redman Lusher, there are currently 200 Rock Choirs nationwide, with some 5,000 members.
If there isn't a Rock Choir operating near you now, there will be soon. Do you want to sing at the opening of the Olympics? Then sign up - chances are they will be there, singing their hearts out to a standing ovation.
The album - their first - is fun, a bit raw in parts, but undeniably feelgood and infectious. What it can't give you is the spectacle. To take part in Britain's biggest choral movement, or to be part of an audience, is a visceral experience, as hundreds of ordinary voices blend to produce one extraordinary wall of sound.
The songs are upbeat, yet audiences leave wiping away a tear. Members find themselves teary-eyed at rehearsal, as 150 right arms are raised as one and fingers start clicking on the offbeat to, let's say, Amy Winehouse's Valerie. The elation generated, says its founder, can be life changing.
Caroline is a force to be reckoned with. She is obsessive, a perfectionist and driven, but she's also warm and nurturing.
'It's not just about singing,' she says, 'it's about emotional wellbeing, making people feel good.'
'When you leave after a rehearsal, you're grinning. You sing in the car. You can't sleep. I do a morning session and the whole day feels amazing'
Men love her too, especially those waiting at home for their Rock Choir wives (96 per cent of members are female). 'They tell me that their wife is a different person since she joined,' says Caroline. 'They say she's alive again, confident; she's lost weight, she's buzzing.'
There's more than a touch of the evangelical to Rock Choir's high-energy rehearsals, and members can have a fervour akin to born-again Christians.
'When you leave after a rehearsal, you're grinning,' says Jan Glynn, 41, a member of the Guildford choir. 'You sing in the car. You can't sleep. I do a morning session and the whole day feels amazing.'
Choirs are enjoying a renaissance. In the City, choral societies attached to banks are seeing numbers swell, even as employees are shed. Singing is cheap, sociable, and clinically proven to relieve stress. Caroline would like Rock Choir sessions to be prescribed on the NHS to help depression.
'I'm not saying everyone in the choir is a depressive,' she says, 'but there is a lot of it about - depression, cancer and divorce.'
Yet this is not what you see on the faces of members as they rehearse. Joyful, Joyful is one of the choir's favourite gospel songs, and it seems to accurately describe the experience.
'Fill us...' they sing at the 8pm session at Hampstead in west London, hands clapping as they step once to the right, once to the left. 'Fill us... Fill us with the light of day'. 'Well, it's better than sex, isn't it?' says one member.
Surprisingly, Caroline is not the product of pushy parents and theatre school. At the age of four she was standing up in front of her class leading the hymns. At 11, she won a music scholarship to St Martin's, an independent girls school in Solihull, West Midlands, where she told teachers she was going to be a pop star.
'Everything I did was intended to get me to London at 21 for a record deal,' she recalls. 'The Grade 8 piano and violin by 15, the degree in popular music at Salford University, playing and singing in bars and clubs.'
But London turned out to be 'an awful experience'. Caroline encountered the seamy side of the music industry, the 'dreadful people on the fringes' who expected an attractive 20-year-old girl to do whatever it took to get noticed.
'I couldn't deal with it. My morals wouldn't take it.' The last straw was when her father, Dave, came to see her singing in a club and was shocked by how low she was. He said, 'You look so ill. You need to leave London and rethink your career.'
So taking his advice, Caroline moved to Farnham where her parents live. For the next six months she was so depressed she couldn't even bring herself to listen to the radio. Then she got a job teaching music at Farnham College in Surrey, and it was as if a light had switched on inside her.
Four years later, when Caroline was 30, she started a choir for her students. It became so popular that soon local people were asking to join, so she set up another choir. Within three years there were 12 Rock Choir groups across Surrey.
Because the members are amateurs and most can't read music, they learn by rote (repetition, not sheet music), rehearsing harmonies and choreographed movements to the sort of hits everyone knows and impulsively sings along to, such as Walking On Broken Glass, Rescue Me, Waterloo. It doesn't matter if you've got a voice like a goose with laryngitis; it's all about taking part.
Then, last year, a journalist who had joined the choir wrote an article about it and things snowballed. In April 2009, the choir was invited to perform on BBC1 Breakfast. Half an hour later, Caroline took a phone call from the head of Decca, part of Universal Music.
'Whatever you've got,' said Dickon Stainer, 'we want to bottle it.' He was offering a four-album deal. Caroline signed a contract at 9.30am the next day in the lobby of a hotel in Farnham. Then, in a trance, she popped across the road to Sainsbury's, 'to pick up something for supper. And then it hit me. I screamed in the aisles, "We've got it! We've got it."'
With no recording studio able to accommodate such a large numbers of singers, Decca hired a school in Cranleigh, Surrey and sent a recording truck. Then, over four days, 987 people aged between six to 70 made an album together.
They recorded in shifts of 250. 'I didn't audition them,' says Caroline, who is scrupulous about inclusivity. 'Everyone had to have the opportunity.'
Although Caroline was reluctant to sing any of the solos - 'Because Rock Choir isn't about me, it's about them' - the album's producer was insistent.
The story of how Rock Choir: Vol 1 stormed the charts is classic Caroline. Determined that the album would be a hit, Caroline decided that she had to do something to promote the CD herself.
'It's as if a big iron gate has creaked open, and finally I've been let into the music industry'
'You get one chance in the music industry,' she says, 'and I was not going to let this album flounder.'
Caroline and her guitarist husband, Stuart, sold their home in Farnham and moved in with her parents, so that they could use the money to book the 3,600-seater Hammersmith Apollo for a one-off Rock Choir concert, which took place just last month.
Not only did she fill the stage with 2,500 singers, she filled the auditorium with their friends, family and anyone else who was interested - and everyone was urged to buy the album.
Later that night, Caroline and her team watched Rock Choir: Vol 1 climb from nowhere to number one on the Amazon pre-order chart - past Oasis, past Kylie, past Scissor Sisters and Eminem. It took just seven hours. And there it stuck, or thereabouts, right up to its launch earlier this month.
Some in the music industry scoff that it's a viral marketing stunt that can't be sustained; Caroline prefers to think of it as 'people power'. It is the people's choir, after all - why shouldn't buying their own album count? Enthusiastic reviews in the press have ensured it will reach a wider audience.
For Caroline, getting the album deal has lit a fuse. 'It's as if a big iron gate has creaked open, and finally I've been let into the music industry.'
Following the recording she was asked to sing lead vocals on a track for the album Coming Home by The Soldiers, the group made up of three real-life soldiers. The album went double platinum, and her version of Against All Odds became the most downloaded song. And when The Soldiers went on tour earlier this year, Rock Choir was one the support acts.
Simultaneously, the Rock Choir business is booming. So many new choirs have been formed that she has had to create a training programme for new leaders. It's all happening so fast - and Caroline is a woman who finds it hard to let go. Her husband and father have been drafted in, and there is literally no escape from work.
'It's bittersweet,' she says. 'Stuart and I work until 9pm, then eat Rice Krispies for supper. I would like to start a family, but there's not a chance it will happen right now.'
Sadly, Caroline's health has suffered. Just before she was due to go on tour with The Soldiers, she was admitted to hospital.
'I'm quite a calm person,' she says, 'but I think I must have been internalising things. I got such horrendous headaches, I ended up in casualty and was put on a drip. I said to the doctors, "I'm going on tour in two days - give me some drugs."' An X-ray revealed an infection on her jaw.
'I think it was a warning. My body was trying to stop me from singing.' But, being Caroline, she ignored the warning and sang at the Royal Albert Hall on a cocktail of drugs, followed by the Birmingham Symphony Hall.
'I was smiling even though my face was killing me. I didn't want the choir to know anything was wrong.' An hour later she was back in casualty. 'In five years I've never missed a rehearsal, but at that point I thought OK, I've just got to go with this.'
The future, she hopes, will be 'nothing less than rock 'n' roll'. 'I'd love to take Rock Choir on a tour of America. Imagine all these British middle-aged women leaving their husbands and children behind and going on tour,' she laughs.
And then there is the 2012 London Olympics. Nothing has yet been discussed formally, but could Rock Choir be Britain's response to the astonishing, synchronised drumming by thousands in the Beijing stadium in 2008?
So concerned are the purists about the 'threat' of Rock Choir that, according to an insider, the organisers of the opening ceremony have already received dozens of letters strongly against this populist act getting any exposure.
'It's their problem,' shrugs Caroline. 'Pop music brings so much pleasure to so many people. You can see what's happening with Rock Choir, that it's becoming a musical movement across the entire country.'
It's hard to deny that the spirit of Rock Choir - in all its all-inclusive, high-energy joyfulness - has a refreshing echo of the original Olympic ethos. As they say, it's not the winning that counts. It's the taking part.