Presented with an album of improvised music containing just two tracks – one 30 minutes long, the other 20 – can cause the heart to sink.

Often, we get the kind of extended free-for-all that's enormous fun to do, frequently thrilling to witness but frankly, boring to listen to. Thankfully, when delivered by experienced improvisers such as these, that's not an issue. The key, of course, is listening, and that's something these musicians clearly do: what impresses most is the way in which no mood or movement outstays its welcome.

The longer opening track moves through multiple episodes – from a quiet, tentative accumulation of small sounds through shrill shrieking to more abstract and exploratory shapes – with all personnel exactly knowing when to drop out and let others take the weight. So, along the way, we get a drum solo from Prévost doing his best Max Roach impression, Wilkinson wailing on alto with Moore spooling out some taut Sharrockisms, and Edwards scraping abrupt arco swoops, before it all finally returns to a quiet bed of small sounds. The second, slightly shorter improvisation has Wilkinson replacing alto with baritone and is, of course, both exactly the same and completely different to what went before.