The main part of this newly unearthed treasure (all but two short, undated pieces) is a live recording of an intimate gig played four decades ago in Goldsmiths College, south east London. In the intervening years, two of the players that made up the trio (Bailey and Rutherford) have died, and improv — then a relatively new development — has evolved through different phases, dabbled in minimalism, accommodated the laptop, and so on. But what you have here is three of the finest and most lastingly influential first-generation free-improvisers, in the full bloom of life, revelling in the sport and play of their chosen (non)idiom. Indeed, while, to the initiated, this could sound forbiddingly serious (and it's not hard to picture the scowls of concentration that must have accompanied this performance), there's actually a great deal of joy and, yes, freedom, in the subtle gestures, hinted actions and disguised responses that make up the delicate interplay at work here. Effectively increasing the available recordings by Iskra 1903 by a third, this is a valuable find.