KATHERINE MACALISTER delves behind the scenes for a peek at the winning formula that is Sing-a-long-a Sound of Music.

WACKY’S our middle name,” Sing-A-Long-A Sound of Music’s Simon Thomas tells me, and he’s not kidding.

We all know about the Nazis, plumbers and nuns, but a ray of sunshine, brown paper packages wrapped up with string and a team of carburettors?

“Yes, the costumes still amaze me,” he says. “Because the amount of effort involved in making them is staggering.

“In the US a whole class of children were running about with a huge green sheet covering them and I suddenly realised that ‘the hills were alive’,” he laughs.

“The carburettors foxed me too until I remembered the scene where Christopher Plummer and Julie Andrews are trying to fix their car,” he says, “but how random is that?”

Simon has been with Sing-a-long since it opened in 1999 and hit an instant chord with audiences all over the world, playing to packed houses across the globe from the Hollywood Bowl in Los Angeles to open air gigs on Hampstead Heath.

But its success was as much of a surprise to them as everyone else.

“It sort of chose us,” Simon says. “We tried it out at four gigs which all sold out and then it just gathered momentum and has been going ever since.”

And 10 years later Sing-a-long-a Sound of Music is still at the top of its game and coming to Oxford’s New Theatre on Sunday.

But what is it exactly that we love so much?

“ Well The Sound Of Music film is beloved around the world. And secondly people love the chance to sing communally – now that people go to church less there is a real need for communal singing.

“Blokes do it at football matches but otherwise people come to us to sing their hearts out. So you could call it a social phenomenon because it fulfils a need,” Simon explains.

For those of you still in the dark, let’s start at the very beginning (a very good place to start).

Sing-a-long-a Sound of Music is a screening of the classic Julie Andrews film musical in glorious, full-screen technicolor, complete with subtitles so that the whole audience can sing along.

The fun-filled show starts with a vocal warm-up led by the evening’s host, who also takes the audience through their complementary ‘magic moments pack’, containing props to be used at strategic points throughout the film.

Then of course there’s the famous fancy-dress competition in which everyone who has come in costume is invited on stage to show off their fantastic tailoring skills.

“The rule is, there are no rules,” Simon says.

“It’s all about the audience.

“So fancy dress is not obligatory but highly recommended and you can either watch or take part.”

The Sing-a-long phenomenon has now spread to include Abba, Joseph, The Rocky Horror Picture Show, Hairspray and hopefully Grease, but its bread-and-butter is still The Sound Of Music.

“It’s so upbeat. And that’s what we are really about. People leave feeling uplifted and happy.”

Sing-a-long-a Sound Of Music will be at the New Theatre on Sunday. Box office on 0844 8471585.