I got the offer to be part of the FIA-orchestra ending Vindöga festival at Sandvikens Konsthall this year and I of course accepted. The orchestra performed improvised music according to the following concept (or rules):
I'm not sure where this concept has it origin but it sure made for some interesting sounds!
Below are photos taken by Christina Wannberg of the orchestra.
Christina Wannberg documented it all and you can find a lot more very nice photos from the whole festival right here: http://www.flickr.com/photos/55769827@N06/sets/72157631718623889/