IF YOU look round the back of Pitlochry Festival Theatre, you'll see what looks like a shed appended to the building. It's sealed with plastic and you can just about make out some kind of plumbing inside. Not much to look at, but it has a crucial role. "This is the real swimming pool," says head of production, Steve Carlin, somewhat improbably given that it looks nothing like a swimming pool.
What he means is that while the audience is enjoying Alan Ayckbourn's Man of the Moment, in which the actors have to fall into the pool of a Spanish villa, the mechanism to keep it all going is out here. If the punters on the front-row get splashed, it will be with clean water thanks to the filtering going on outside.
"If we put the heating, filtration and chlorination units on stage it would be so heavy we'd never be able to move it," says Carlin. "This way, we just wheel the empty pool in place. We can fill it with 17 tonnes of water in 20 minutes."
In isolation, this technical achievement is impressive enough. But when you remember that Pitlochry operates a repertoire system with up to six plays alternating on a nightly basis, it's little short of staggering.
Ken Harrison's design for the Ayckbourn play is one of those eye-popping spectaculars that accounts for the audience's tradition of applauding before the show has even begun. It's a reproduction of a Mediterranean patio built with the same attention to detail as the real thing. Plus it has to be pulled apart in less than two hours and stored away every night - leak-proof swimming pool and all.
The same goes for the whole Pitlochry operation. Leave aside the bewildering detail that a picturesque Perthshire town is home to Scotland's second-most attended producing theatre (only Edinburgh's Royal Lyceum can beat its 64,000 audience figures) and consider the strategics involved in programming six plays, four of which open in quick succession, for a single company of 18 actors.
Few can appreciate the level of forward planning it takes. If artistic director John Durnin hasn't settled on his programme for summer 2007 by the time you read this, he will be behind schedule. Carlin and his team will be in similar trouble if they haven't built two-and-a-half sets by Christmas. And the costume department has to imagine they're working on one massive play that just happens to take place in four different eras.
Any decision that Durnin makes has repercussions right down the line. He's been wanting to include Man of the Moment in the programme for the past couple of seasons, but only with this year's combination of plays - a Christie, a Wilde, a Wodehouse, a Steinbeck and a Shakespeare - has the technical department felt it possible.
"All six plays are interlocked," says Carlin as we walk around his hangar-like workshop. "John tries to balance titles and I try to balance three-dimensional objects."
If he can't fulfil three criteria - to get the set looking the way the artistic team wants, to turn it around in two hours and to fit it into the allocated dock space - he has to tell Durnin it won't work. "We decided we couldn't do Man of the Moment last year because of the scale of the other shows," he says. "We have high production values and if we're going to do something we do it properly."
"Pitlochry tests everybody's craft skills more than any other theatre I've worked in," says Ben Twist, the director of Man of the Moment and A Woman of No Importance. "The difficult thing when we're casting is you see someone who's great for your role and then they're terrible at one of the others. We have to look harder and the actors have to be versatile."
For all these reasons, the Scottish Arts Council appears to have missed a trick in turning down the company's recent application for extra funds to develop a formal training system for actors and crew that would benefit the whole of Scottish theatre.
"NEW ACTORS always say to us they get more from doing a season here, than all their years at drama school," says general manager Nikki Axford. "We wanted to extend that through to the theatre crafts - wardrobe, carpentry, scenic artists - because it's a particular strength we have."
The SAC decided Pitlochry had been so successful in attracting audiences that it didn't need any more money. "We felt they didn't understand what Pitlochry's all about and made some pretty crass generalisations about our audiences," says Axford, pleased all the same by the SAC's proposal to pay off the company's historic deficit.
Now, as the first preview performances nears, you can guess how the tension will be mounting. Within the space of a fortnight A Woman of no Importance, Summer Lightning and Man of the Moment will have opened, and Chimneys will not be far behind.
In the caf, actors Karen Davies and Michelle Gallagher are swapping notes. Having to rehearse one play in the afternoon and another in the evening is all part of the fun.
"I loved every minute of it last year," says Davies, whose three roles include the lead in A Woman of No Importance. "I used to know what play we were in by the colour of my tights on the dressing room table. I'm the last generation who did monthly rep and I like the old way of working where you get to stretch yourself. It keeps you on your toes."
Pitlochry Festival Theatre (01796 484 626), preview performances from Friday until June 5, the season runs from June 6-Oct 21