The Seattle Improv Meeting is a group dedicated to exploring structured improvisation. Utilizing graphical, textural, Flash, verbal and other non-idiomatic scores the group examine the intersection of composition and improvisation. The group primary focus has been Cornelius Cardew’s epic graphic score Treatise (we already post about it) which they currently are in the midst of a complete playthrough, at the rate of 4-6 pages per session (due to the lack of any explicit time scale, the Treatise can also be played in parts, al least a page at a time).
On the site you can also find a guide to Treatise with many materials and links.
Here is the last session (08/08/2006) concerning the pages 23-26.