WHETHER the expression is still in use, I cannot say – the language of the business world, and particularly the service industries, is more susceptible to fickle fashions than a self-obsessed 15-year-old – but tourism theorists used to speak of “the shoulder months”, those being the ones on either side of the peak summer season. They have long been a target for the promotion of Destination Scotland, doubtless because to many of us who live here all year round it seems that the weather in spring and autumn is often more dependable than during what passes for a summer.

It is certainly true that nature is often at its best, with shows of bluebells and daffodils on country house estates in the spring, and the turning leaves of Perthshire woodland in the autumn making it a worthy, if less extensive, rival to New England in the fall.

Pitlochry Festival Theatre’s summer season continues until next Saturday, October 14, and is then swiftly followed by Peter Arnott’s new adaptation of Compton Mackenzie’s The Monarch of the Glen, in the new “Scottish” slot in the theatre’s calendar previously filled by Para Handy and Whisky Galore.

Director John Durnin’s initiative is in part built on the success of an outdoor show that has been attracting tourists to Pitlochry in October since 2002. The Enchanted Forest is a sound and light event in Faskally Wood that has effectively extended the pretty Perthshire town’s season by another lucrative month.

Initially produced by outside agencies on the Forestry Commission’s loch-side site, when commercial interests looked like giving up on it, it was rescued by the local community and is now run by The Enchanted Forest Community Trust.

Faskally Wood, which lies on the other side of the loch above the Hydro-Electric Dam and Fish Ladder that are the theatre’s near neighbours (and which boast a fine new Visitor’s Centre), attracts 70,000 visitors over the year, as a very fine place for a walk with a wide variety of evergreen and deciduous trees. The Enchanted Forest more than doubles that number in a single month, proving that art can always enhance even the finest works of nature.

In previous years, the event has often had an over-arching theme with a one-word title (Absorb, Shimmer or Elemental), or suggested some vague narrative like the arrival of visitors from Outer Space. This year it is much more like an outdoor exhibition, a figure of eight journey through a programme of installations to feed the eyes and ears. It is a nice touch that this programme starts on the bus out to the site, with nine-year-old Robbie Low’s safety and information spiel the result of him winning a radio competition – a career in broadcasting is surely the Broughty Ferry lad’s for the asking.

Because different sound and lighting equipment, water features and props are installed each year, The Enchanted Forest always looks different, but this year the removal of invasive rhododendrons has completely changed the views on the circuit around Loch Dunmore. Hence the title Oir an Uisge, Gaelic for Edge of the Water, as the reflective vistas that are key to the event’s success are opened up. Introducing rain-curtains on the bridge and a canopy of coloured umbrellas may be funnier on some evenings than others, but details like these, the Digital Rain of Chris Dodds and Lightworks fibre-optic Liquid Sunshine, soundtracked by Rachel Cullen, are elements not to miss. The big stuff, like the title piece and the closing Belisama, are the work of lighting designers Kate Bonney and Simon Hayes, with sound by RJ McConnell and Jon Beales, and the whole creation has been produced by Zoe Squair.

It is as fine a visual art exhibition as you will find in Scotland at the moment, and works on the other senses as well. Keep your ears tuned as you watch to catch Juliet Cadzow narrating Ann Marie Di Mambro’s story of The Urusaig, and you may wonder what else – besides a lot of clever plumbing and cabling – may currently be lurking in the loch.