Late for her rehearsal, a lady still wearing her cycle helmet canters through Friends House, the Quakers' historic headquarters in London's Euston. "Which choir are you with?" she asks. I tell her I'm a reporter. "Ah," she says, breathlessly. "I'm a GP, but it's so difficult to get here straight from surgery."
I follow the doctor into a huge, galleried, wood-panelled meeting hall, and am suddenly stopped in my tracks. The exalted cries of Mahler's Symphony No 8, "Gloria sit Patri Domino" ("Glory be to God the Father"), fly from 400 choristers' mouths and punch me in the gut. It's a triumphant, almost transcendental sound, part of a rehearsal a few days ahead of this evening's opening night of the Proms. It's an especially impressive spectacle when you consider its origins: hundreds of the assembled choristers – including the tardy medic, Margaret Ellerby – hold down full-time jobs, performing phenomenal vocal gymnastics in their spare time. They are part of the Crouch End Festival Chorus, a collection of amateurs drawn from a five-mile radius in North London.
The group started in 1984 with a few recruiters handing out leaflets at supermarkets. Their subsequent rise from anonymity to national prominence has been swift – and spectacular. On Friday they are set to perform in front of 5,500 people in the Royal Albert Hall and up to one million viewers on BBC2, for the biggest event in the classical music calendar.
"Thankfully, there are enough good people around so I don't have to do everything," says Ellerby, speaking from her surgery the following day. "I can't do a lot of the recording sessions in the evenings because of my job. But I find music challenging and relaxing. It uses a different bit of your brain to work. You forget about everything else bothering you. The exhilaration you get from a Prom is wonderful. You end up on a high for several days. Even a rehearsal can be quite exciting."
The vocal dry run melds Crouch End's massed ranks with the BBC Symphony Chorus, who will be joined on Friday by choristers from Westminster Abbey, Westminster Cathedral and the Sydney Philharmonia. But Crouch End's elevation into the limelight is the most impressive. Having never enjoyed the backing of a major religious institution or broadcaster, they were set up by former chorister David Temple almost 20 years ago when "local choirs were dying a slow death", and now regularly appear at the Barbican, Hampton Court, even Glastonbury. At Worthy Farm last month its choristers issued a classical counterpoint to The Kinks' Ray Davies during "Waterloo Sunset", as 60,000 revellers looked on.
Freelance television producer Duncan McAlpine says: "It's not very cool to be in a choir but it's so cool to be in this one. When Ray Davies was singing about Kinks' bassist Pete Quaife, who had just died, he was close to tears. It was a once-in-a-lifetime experience."
Crouch End's membership is diverse. There is Johnny Mindlin, the sound engineer who looks like Jimmy Page; wine company employee Maggie Huttingford; teacher Jonathan Chutor; Carole Elphick, a clergywoman; even Dame Liz Forgan, chair of the Arts Council.
The popularity of amateur choirs has been boosted by television shows like The Choir, the third series of which was broadcast last year. The programme sees choirmaster Gareth Malone polish the voice boxes of amateur singers in suburban towns. It has won two Baftas. There are 26,000 people affiliated to 500 amateur choirs around the country, according to the National Association of Choirs.
"Crouch End are a decent and busy amateur choir in the long tradition of decent and busy British amateur choirs," says The Independent's classical music critic Edward Seckerson. "They have always been the backbone of musical life in this country – partly out of financial necessity and partly out of our love of communal activity. Doubtless the Gareth Malone TV programmes have led to a rise in community choral groups."
Being part of such a chorus is no small commitment. The Crouch End group, comprising 150 singers, 133 of which will appear in the Proms, normally meets weekly on a Friday night. Generally there is a second meeting during the week; the weekend can be taken up with recording sessions (the choir's Kinks Choral Collection, another collaboration with Davies, reached No 9 in Amazon's charts last year; a recent recording with soprano Kate Royal, Midsummer Night, was nominated for a 2010 Grammy Award). For the Proms, the choir has had seven rehearsals on its own, plus five with the other choirs.
Temple says the secret to his success is "building up enough dosh to put on great concerts and maintaining the choir's standards". He adds: "A lot of organisations reach a peak and then decline, whether its football teams or arts charities. Getting to the top is hard but staying there is harder," he says. "The other challenge is getting people to come and hear live music. A lot of people don't have a clue as to how powerful it is. The massed voices hit you like the bass at a rock concert. It's just as impressive."
Like many amateur choirs it suffers from ailing male membership. "A lot of choirs are struggling to find 10 men," continues the choirmaster. "It's because historically it's seen as a girly thing to sing classical music. But at Glastonbury you could hear 100,000 people of both sexes singing to Muse. People have the ability but a lot of men have had it drummed into them that classical music is sissy."
No such problems for Crouch End; its participants are all committed and great friends – they often disappear to the pub once they've stowed their songsheets. "It's just like cookery programmes have resurrected interest in cooking, so choir shows have highlighted the fun to be had in breaking your bread and sharing a passion," continues McAlpine. "Everyone has a voice and it's surprising how easily you can find it."
That, however, comes after ironing out all the creases. On Monday night, Temple was joined by BBC Symphony Chorus director Stephen Jackson to forensically analyse the throng's cries, tearing apart every bar of Mahler's intense, ear-splitting, "Symphony of a Thousand", so named because of the power it demands.
"The sound is so exciting," concludes Temple. "But we have to get everything better. As chorus masters we have to ignore how good it sounds and pick holes in everything. You end up with utter perfection. It is very high energy. When we get together with an orchestra that will produce adrenalin of its own. It will be very loud. Almost like being in the trenches."
Charles Mackerras, 1925-2010
Sir Charles Mackerras, one of the most radical and influential conductors of the last century, has died of cancer aged 84. He was most noted for his preoccupation with Mozart – his final performance was conducting Cosi fan tutte at Glyndebourne last month – and for introducing the work of the Czech composer Leos Janácek to Britain in the 1950s, having stumbled across it as a student in Prague.
Born in New York to Australian parents, Mackerras became known for his ferocious delivery, his work ethic, blunt criticism and humour, and particularly for his experimentation. In 1959, he famously gathered "every wind player in London" for a midnight session to play a bellowing version of Handel's Water Music – just as the composer had intended, and in contrast to the usual ambrosial style. He led the Sydney Opera House's opening concert and directed English National Opera and Welsh National Opera. Mackerras was due to conduct two Proms in this summer's season. A Prom will be dedicated to him.