When Ultras vocalist and former Over The Wall lynchpin Gav Prentice says of the massive drum kit sitting between him and his fellow band member that it is there not for them to play, but to provoke the audience into some interactive horseplay that "breaks the fourth wall, as we say in the trade," he inadvertently sums up the spirit of Hidden Door's nine-day DIY festival of music, theatre, art and film, which ended last weekend.

The drums actually belonged to Stealing Sheep, Friday's headlining band at regular live music night Limbo, housed offsite in the Bongo Club. Stealing Sheep's female trio were equally conceptual, and not just for their audacious mix of martial mediaeval chorales and electro pop, but for the way their assorted colour-coded leads and cables matched their rainbow-hued hosiery.

However, it was within the sprawl of Hidden Door's main multi-space venue - a courtyard just off King's Stables Road in a former City of Edinburgh Council building that has just been flogged off to property developers to build yet another luxury hotel - that interactive walls were really broken down.

This was certainly the case with local companies Creative Electric and Do It Theatre. While Creative Electric's ice-cream based durational piece, Treat, threatened to break out into a food fight amongst the audience as its two young performers revealed snippets of information about themselves, Do It Theatre's Creature was a participatory piece of storytelling designed for people with autism.

Created by writer and cartoonist Steven Fraser and educationalist Ewelina Rydzewska with support from the Tom McGrath Trust, Creature invited an audience of seven into a small room lined with the diaries and drawings of the narrator of a script we were handed at the door, and which we were instructed to read in silence. An example of what Do It describe as 'private plays', the result was an intimate and very personal meditation on autism.

In:Humanity was a devised piece by Melanie Phillips and Leonie Rae Gasson which explored how much technology runs and potentially ruins our lives through an extended game involving an imaginary app. Presented by the young Produced Moon company, Phillips and Gasson again attempted to break down the artificial divide between audience and performer.

Katrine Turner worked in similar territory with Magia, a solo piece in which Turner got the audience to fill in a questionnaire before showing off her rudimentary magic skills in between engaging in online chat. Out of this, the whole notion of what constitutes physical and virtual reality was challenged in a strikingly low-key meditation.

Elsewhere, teine eiginn / need fire was a 10-minute exploration of ancient fire festivals created by Dougie Strang in association with sound artist Nic Scrutton and performed by students from Fife College's Summerhall-based Physical Theatre Practice course in a purpose-built hut to an audience of seven.

The End And The Beginning was a 15-minute piece in which different performers reacted to a film of barren landscapes. Created by the Edinburgh-based Darkland Collective's core trio of Yulia Kovanova, Kenny Lam and Igor Slepov, the likes of performance artist Jean-Francois Krebs reacted from behind the screen seen only in shadow as French horn player Matt Gio, electronicist Yoann Mylonokos and a myriad of others conjured up impressionistic soundscapes to match the mood.

It was the rolling programme of a daily lunchtime event called Unforeseen, however, which defined the random, messy and anything-goes attitude of Hidden Door. Under the auspices of five local grassroots arts producers, artists Hans K Clausen, Charlie Knox and Martin Sweeney initiated an interactive digital sculpture made up of found objects including a zimmer frame, a showroom dummy and assorted vases, boxes and mirrors. These then had sound and projected vision added to the mix through a technical set-up brought to life when the audience joined hands to form a chain.

This then prompted a series of guest artists to add their own input which by turns deconstructed and reconstructed the nature of what constituted the very essence of performance. So while Catherine Street and Jennifer Williams became a kind of Greek chorus conducting a set of cyber-tribal beats and loops, Jessica Ramm enabled the audience to square up to each other in an origami-based play-fight. Anne Marie Shilito took notions of connectivity and community even further, with the audience going along willingly at every turn.

What this artistic group hug was tapping into was an ongoing trope picked up by a newish generation of theatre-makers and indeed audiences who aren't prepared to be kept in the dark while something is acted out in front of them, but want to be part of the action and help make a scene themselves. Whether consciously or not, Unforeseen explored ideas about play first presented by Peter Brook in his seminal 1968 book, The Empty Space.

All of which transformed Hidden Door into a fun palace fuelled by a loose-knit idealism which is currently thriving despite the local authority's every attempt to demolish it.

For ongoing information about Hidden Door, go online to www.hiddendoorblog.org