Opera in a tent? It's one of the attractions of a garden staging of 'Così Fan Tutte' with a Raj theme, along with some promising young singers, writes Arminta Wallace

'I feel," says Nicholas Heath, sipping his coffee and offering a beatific smile, "that there ought to be a lot of sex in this show." What? I mean, sex rears its head in Così Fan Tutte, Mozart's operatic tale of couples behaving badly, but we're not talking upfront and explicit, are we? Stuff to frighten the horses?

Heath, the director of Opera à la Carte's "garden opera" production, which played at Loughcrew, in Co Meath, a fortnight ago and moves to Woodbrook House, near Enniscorthy in Co Wexford, for two performances this weekend, looks shocked. He is, he explains, thinking more of sexual suggestion. Hints and allegations, surreptitious eye contact, that sort of thing.

But, he adds, he has taken the liberty of adding an extra character to the plot. What? Meddling with Mozart? Downgrading Da Ponte's libretto? "Heavens, no. It's a non-speaking role," he explains hastily. "Just a little something to spice things up." "It" turns out to be a hunky actor by the name of Ishwar Mahraj, who shimmies in and out of the action looking good enough to eat; a nice theatrical touch in an opera that once had the reputation of being more than somewhat misogynistic.

It's also a reminder that although this may be Così under canvas - and Heath is aware of the many heady attractions of garden opera: the picnic on the lawn at the interval, the big-house backdrop, the posh frocks, the champagne - it's vital to get the artistic part right if the production is to succeed.

First, and most importantly, comes the casting. As a full-time member of the chorus at the Royal Opera House at Covent Garden in London, Heath is well placed to get hold of the most promising up-and-coming young actor-singers. For this production they are Gudrún Ólafsdóttir, an Icelandic mezzo who has just won the Kathleen Ferrier Song Prize at the Wigmore Hall, and Jochem Van Ast, a Dutch baritone who has already sung all sorts, from Rossini's Figaro at Loughcrew last year to, according to his biography, the role of a bearded transvestite.

Next comes the staging. After a decade of putting on outdoor opera, Heath has developed an instinct for what works best in a sylvan setting.

"That first year at Loughcrew we did The Marriage Of Figaro," he says. "It's a marvellous opera to start off with; it's a comedy, and it's all about reconciliation and, of course, it's all in a garden as well. So off we romped. And then I suggested that we might do something darker, so we did Rigoletto. Which, of course, is quite funny up to a point, but then it turns - the whole thing spins - and it gets pretty violent.

"But in this sort of intimate setting the final act was extremely powerful. A lot of people came away going, wow. They were genuinely moved."

Last year came a "tango" Barber Of Seville, the bright and breezy score arranged for clarinet, accordion, bassoon and piano. "The intention is to give people a different feeling every year. But it's about more than just words and music. You have to make it a theatrical experience as well."

Which, on its opening night at Loughcrew, Così Fan Tutte undoubtedly was. Members of the audience who had been a little too liberal with the early-evening champagne must have been startled when they entered the performance marquee to find it rigged up as a boxing ring and the opening scene played as a sparring match between tenor and baritone, dressed in shorts and sleeveless vests.

Heath's setting, a British garrison in India just after the first World War, establishes a sunny, languorous mood that cleverly links to the outdoor-opera vibe. "I don't modernise things for modernising's sake," he says, "but there were uprisings in the early 1920s in India, so the idea that the boys were stationed there and could just be called up at any minute made sense."

He is acutely conscious that the opera demands tightly choreographed ensemble playing. "When you get a team of people together to put on a production you never quite know what the chemistry is going to be. There's a big difference between how people present themselves at audition and how they are in real life. You know, they look beautiful for the audition, and then they turn up for rehearsal in a smelly T-shirt.

"But this group has been on a real journey through this opera. We've had some pretty hot discussions about how other people view Così and how I view it - and I think it has become an education for all of us."

For James Edwards, whose snazzy shades suggest he has never been within a million miles of a smelly T-shirt, it has certainly proved so. This outing as Ferrando is his first Mozart role as a tenor, having moved up from the baritone register just two years ago.

"It's pretty unforgiving, this music," he says ruefully. "Bohème and La Traviata you can shout your way through, but you can't do any shouting in this. You've got to sing it. I usually spend my summers doing session work, which pays a lot more, but my teacher thought this would do me good. We'll see."

In September Edwards is due to begin a two-year stint as a Vilar artist at Covent Garden, which means he'll be paid a full-time salary to sing small roles and understudy big ones, with free coaching from top visiting artists such as Plácido Domingo and Luciano Pavarotti thrown into the mix.

"Meanwhile I'm having a wonderful time here," he says. "I've eaten tons and tons of food, and I'm staying in a castle in a four-poster bed."

Diane Atherton, a soprano, is a regular with Opera à la Carte. "I did Susanna in The Marriage Of Figaro and then Gilda in Rigoletto, and then last year I had a baby," she says. She, too, will be moving on in the autumn: she is planning to emigrate to the US with her conductor husband, who has just been appointed artistic director at Washington Cathedral.

"Garden opera is difficult," she says, "because it's opera in the round - and the audience is right there, a foot away from you. But as a young singer you have to learn to be flexible. Otherwise, quite frankly, you'd never get any work. Very few singers walk straight from college into the main theatres."

While we're talking a young man in a baseball cap - stage manager Benjamin O'Grady - drifts in and out, bearing strange offerings. A bucket of water that, to everybody's bafflement, has sprung a leak. A handful of trainer laces. Heath regards the latter somewhat dubiously. "Hmm. Bit pink, aren't they?" O'Grady, who is studying stage matters in Stratford-upon-Avon, no less, vanishes again. It is, after all, opera outdoors - and you have to be ready for anything.

"Ah, yes," says Heath with another of his unflappable smiles. "The generator failed last year. The boys had just climbed into Rosina's apartment after the thunderstorm scene. I was on the lighting board, and during the thunderstorm the lights were flickering, and I was looking at it and thinking, what's going on here? What have I touched?

"And then the whole thing just suddenly went ummmmm and everything went dark except the oil lamp which the boys had on stage. The band, naturally, stopped - although the pianist, a répétiteur from Covent Garden who knew the score inside out anyhow, kept on playing.

"And Jochem just looked over towards the piano and whistled a little bit, and then started singing Some Enchanted Evening. It brought the house down."

• There are some tickets left for Opera à la Carte's Così Fan Tutte at Woodbrook House tomorrow night and Sunday night. Bookings on 054-55938