WHEN Leith Theatre opens its doors as this year's home of the Hidden Door arts festival today, festival director David Martin believes it will be twenty-five years to the day since anyone performed here. This was only discovered by accident when sound artist Dave House was researching a new work designed to mark what he calls the venue's "melancholy-yet-beautiful state of disrepair". Working in situ, House will use field recordings and environmental sound in an attempt to evoke the past, present and future of the building for a piece that will run throughout Hidden Door's ten-day duration.

Some of these sounds might well emanate from what happened two days into the festival get-in, when volunteers gutting the main hall discovered what lay beyond the black drapes and what turned out to be a false black proscenium arch. Once this was ripped away, it revealed a far more ornate surround that came complete with an ornate crest at its the centre.

This is just one of the discoveries to be found in this criminally unloved building, which was gifted to the people of Leith by the people of Edinburgh following the decision to incorporate the Burgh of Leith into Edinburgh in 1920. After opening in 1932 as Leith Town Hall, it went on to become a much needed concert hall and theatre utilised by Edinburgh International Festival among others.

With the building now under the care of Leith Theatre Trust, ambitious long-term plans are afoot to restore the venue as a permanent fixture on Leith and Edinburgh's cultural calendar. As Hidden Door's artistic director David Martin moves around the back-stage nooks and crannies about to be transformed into assorted performance spaces, cinemas and galleries, it is clear there are many more discoveries to be made within its walls.

Old dressing room doors are engraved with ornate lettering, with one space decreed the domain of "Female Accompanists", a strict demarcation that couldn't imagine being anything other than a permanent backstage arrangement. Which rooms house Anna Meredith, who plays tonight, or Kathryn Joseph, who will appear next weekend, remains to be seen, but these two Scottish Album of the Year-winners are very different female musicians than those welcomed by Leith Theatre's original managers.

Also appearing on the main stage over the next week will be former Ladytron vocalist Marnie, Lost Map Records duo Manuela, jazz legend Soweto Kinch, the group Idelwild and many others. Elsewhere in the building, artists of all kinds will take advantage of such atmospheric surroundings. Theatre companies Creative Electric and the Ludens Ensemble will present new works, while there will be work-in-progress presentations by site-specific specialists Grid Iron and actor Tam Dean Burn.

A screening of Fritz Lang's seminal science-fiction film Metropolis will feature a new score by Kim Moore, aka Wolf, alongside fellow electronic composers Matt Collings, Dave House and Phil McBride. There will be spoken word from Inky Fingers and Flint and Pitch, plus a special performance of Rules of the Moon, a new collaboration between poet and musician Rebecca Sharp and sound artist Philip Jeck. While Sharp is best known for her work as a playwright at the Arches in Glasgow, Jeck's previous appearances in Scotland have included experimental music festivals Instal and Kill Your Timid Notion. All of which suggests that Hidden Door isn't quite so hidden anymore.

“There's an element of jeopardy about it,” says Martin, sitting in the balcony of the theatre's 1,000 capacity auditorium while a small army of volunteers clatter around downstairs in what resembles a mini building site. “We're upscaling things this year because we've got the space, and it's a big risk, but having somewhere like this allows us to get a lot of people in the building to see a big band in a way that we couldn't do before. It also allows people to move around the building and see all the other stuff going on.”

Hidden Door was an initiative originally begun in 2010 at the old Roxy Art House, now Assembly Roxy, as an attempt to harness some of the artistic activity that was going on in Edinburgh. After Martin took some time out to take stock of that event, Hidden Door returned in 2014, taking over the then derelict row of arches on Market Street. For the last two years it has been located at City of Edinburgh Council's old lighting stores in King Stables Road. All three venues, in their different ways, created a sprawling village of alternative culture which Leith Theatre looks set to stamp with its own personality.

“When we started it was a bunch of artists and musicians, and we called ourselves the Hidden Door Collective,” says Martin. “The plan had been to try and do things in derelict spaces, but that never worked out, and after that it was about just trying to find out where the interesting spaces were, because there's a lot more in Edinburgh than people sometimes think. When we found the arches, the Council initially weren't keen, but after we made a success of that they came to us, and they've been really supportive ever since.”

For a city where a year-round civic enthusiasm for artistic activity hasn't always been apparent beyond its established festivals, this is quite a breakthrough, particularly in relation to what was happening elsewhere.

“I was looking with envy across the great divide of the M8,” says Martin. “It seemed, especially in the early 2000s, that things were happening in Glasgow in a pop-up and spontaneous kind of way that was really exciting. In Edinburgh things were more staid and institutionalised, and there was no real way for artists to get their work out there. You could submit something to the RSA, but there was very little artist-led activity and very little collaboration. I could see how much talent there was here, and I thought there was a more dynamic way of doing things with that.

“Sometimes Edinburgh feels like it's an old lady's house, and once a year in August she'll let you have a massive party that wrecks the house, then everyone clears off, and for the rest of the year the city tidies itself up again until there's another influx. I felt that there was enough talent here to do something the rest of the year, and there were enough interesting spaces around to use them in a different kind of way.”

Since then, Hidden Door has become part of a new wave of burgeoning, if still largely unsung, grassroots artistic activity across Edinburgh that shows it up as a Jekyll and Hyde city. The festivals and national institutions that grace Scotland's capital may get all the attention, but it is off the beaten track that a new generation of artists is laying the foundations for the future.

As well as Hidden Door, the similarly expansive LeithLate festival has just announced its programme for this year, while artist-run spaces such as the Embassy and Rhubaba allow emerging talents to showcase and develop their work. The city-wide Edinburgh Annuale visual art festival does this on a larger scale. Then there is the Forest and an ever changing network of short-lived collectives and pop-ups that put on ad hoc one-off gigs in church halls and social clubs, reclaiming the original focal points for community activity as they go.

Long established organisations such as Out of the Blue and it's sister venue the Bongo Club led the way on this, mixing up art, music and club culture in a way that has fostered an attitude based on self-determination. Now glossy institutions such as the Traverse Theatre and the Fruitmarket Gallery were, of course, born out of the similar spirit of 1960s and 1970s counter-culture.

While Martin acknowledges a certain level of factionalism among Edinburgh's pockets of creativity, such a welter of activity has opened up the city for Hidden Door to become a nomadic cauldron of creativity which is unlikely to sit still for long.

“What we've found is that the people of Leith are really up for stuff like this,” says Martin. “There's loads going on here at various levels in terms of small music venues and other things, but the area doesn't really have a large-scale social hub in a way that Leith Theatre will hopefully become.”

Whether Hidden Door happens in Leith Theatre again is for the future, although Martin expresses ambitions for it to be flexible enough to exist, not just in Edinburgh, but elsewhere as well.

“By doing Hidden Door in Leith Theatre, we want it to feel like something brand new is happening here, and hopefully the people of Leith will get behind it,” he says. "It's exactly the right place to do it this year, but Hidden Door isn't only about Leith. It's for everywhere.”

Hidden Door opens today at Leith Theatre, Edinburgh, and runs until June 4.

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