Arts: The stalls are alive...

... with The Sound of Music. A one-off singalong was the unexpected highlight of last year's Lesbian and Gay Film Festival. Now we all have the chance to climb every mountain

What's the connection between The Song of Bernadette, Sister Act, Black Narcissus, and Nasty Habits? They're all films about nuns. Disregarding the tawdry Nuns on the Run, this disgracefully undervalued genre also includes such performances as Debbie Reynolds simpering beautifully in The Singing Nun, Audrey Hepburn suffering beautifully in The Nun's Story, Helen Reddy singing beautifully in Airport '75 and I don't think we need go into Klosterschulerinnen aka Sex Life in a Convent. But the unassailable Ur-text has to be The Sound of Music. Nuns, Nazis and memorable numbers, what could go wrong? Nothing.

Twentieth Century Fox hired Julie Andrews, tossed in helicopter shots of Salzburg scenery, and the rest is history. Childcare was never more glamorous. "It restores faith in the art of motion pictures," yelped the Hollywood Reporter. "Who says you can't buy happiness? As long as Robert Wise's The Sound of Music is playing you can. And that is going to be for a good long time." How true. You thought the Sixties were summed up by The Graduate, Midnight Cowboy, and Easy Rider? Forget it. The Sound of Music was America's highest-grossing film of the decade.

In Britain alone, the soundtrack album sat at the top of the charts for an astounding 70 weeks. That, together with the fact that the BBC screens it on anityy and every public holiday, means that generations of audiences - often against their will - have grown up singing along to "Do-Re-Mi", "Edelweiss" and (How Do You Solve a Problem Like) "Maria". The truth of this was proved last April at a ludicrously successful, specially subtitled screening of Singalong-a Sound of Music, the brainchild of Robin Baker, co-programmer of the annual London Lesbian and Gay Film Festival.

Having spotted a cinema in Scotland which provided song sheets for a senior citizen showing of Seven Brides for Seven Brothers, Baker realised he knew at least fifty-seven varieties of people who might enjoy a similar event.

Traditionally, the festival's fastest-selling events are movies promising sex and acres of naked pecs. But, as he recalls, "It was a bit of shock when it was wimples and Alpine scenery that seemed to pack them in. And about time too." All 450 seats vanished within 24 hours. On the day, the National Film Theatre was awash with a wholly uncharacteristic number of nun outfits, the odd Nazi officer's uniform and dozens of matching pairs of lederhosen made out of curtains, a dressmaking tip which links the film to the other all-time favourite Gone with the Wind.

The fancy dress prize awarded in the intermission - the film lasts an alarming 2 hours and 54 minutes - by Countess Candy von Trapp (aka performer Ivan Cartwright), resplendent in a pleated pair of knee-length blue brocade curtains complete with curtain rail, was hotly contested. After a vocal warm-up for the audience, we settled back. Within moments of Ted McCord's Oscar-nominated camerawork taking us over the hills, an air of barely suppressed hysteria took hold. Snow-capped mountains gave way to greenery and suddenly, as the music hurtled up the scale, there in the far distance was a tiny speck of a woman in an apron rushing towards us and the entire auditorium burst into applause and began singing.

Swathes of them probably hadn't sung in public since school assembly, but the innate British choral tradition took over. Never has audience participation been such a pleasure. Quite honestly, it was one of the funniest and most extraordinary afternoons of my life, and not just the spectacular moment when it was revealed that the fancy dress winner was a real nun: cue standing ovation.

The audience profile in terms of age, race, gender and sexuality (there were entire families in costume) was an arts marketing dream, but discovering yourself in the midst of a vast crowd - all sharing your sense of humour - made everyone feel more than a little giddy. It wasn't just the songs, either. Whenever the evil Baroness appeared, there was an outbreak of hissing, extended to stupid Kurt who may be seventeen going on eighteen, but he's also a Nazi.

As Baker observes, audience ad-libs were also a highlight. "Towards the end when everyone is feeling tense and a bit peaky, one of the children whispers, `What would the Mother Superior say?' And a dozen of the butcher audience members cried out `Climb Every Mountain!'" Well, you had to be there to get the full effect. Or rather, you didn't, as producer David Johnson was so carried away by it that he fixed up a week of repeat singalong screenings at London's Prince Charles cinema.

Baker is understandably tight-lipped about the wholesale appropriation of his idea into the heart of the commercial West End. All he'll say is, "Imitation is supposed to be the sincerest form of flattery, but I draw the line at plagiarism. Even the publicity copy is lifted from the Festival brochure without credit." Never the less, he's happy that many more will now experience the event's unimaginable pleasures.

Of course, millions of people loathe the film. In 1965, when the great Pauline Kael lambasted it in McCalls, a magazine with a circulation of 8.5 million, she was fired. (Although the editor denied, rather weakly, that this was the reason). But Kael was not alone. "I wish it well," sighed the late Dilys Powell, the former doyenne of British film critics on its original release, "as long, that is, as I don't have to see it again."

Yet this musical's stupendous success has had a dreadful effect on the genre. Most people who say they hate musicals are thinking about this perfectly-confected piece of tooth-rotting sweetness, and on the strength of the subtlety of its dramatic construction - there's not a single unexpected moment in the picture - who can blame them? It may have a well-engineered "Springtime for Hitler" Anschluss plot, but face it, the mucus-inducing tale of a governess falling for her employer is the stuff of a million tired Mills & Boon romances. Technically speaking, virtually the entire score consists of all-too-easily excerpted songs. Integral to the development they're not.

The whole thing is probably the least sophisticated of the 37 shows for which Oscar Hammerstein supplied lyrics. And if you don't believe me, check out "My Favourite Things" which includes the list "Doorbells and sleighbells and schnitzel with noodles." Hang on a minute. I know that nuns aren't allowed much in the way of pleasures but doorbells?

Nowadays, except for Disney's animated mega-hits, the film musical is all but dead. The opportunities for singalong screenings remain with revivals. (Mercifully, no one is going to mount Singalong-a Flashdance... I hope.) The only other true possibility for such treatment is The Wizard of Oz - and if anyone runs with that idea, I hereby stake my claim to 10 per cent of the box-office.

Eight performances at the Prince Charles Cinema, London WC2 from 13 August. Call 0171-437 7003 for details.