It’s an alarming thought that the Spontaneous Music Ensemble’s Karyōbin – widely considered to be a founding document of British free improv – has been available only sporadically since 1968, when it was released on an imprint of Island Records (with Derek Bailey’s name misprinted on the cover as Dennis Bailey). An early 1990s reissue on the Chronoscope label turns up occasionally on Amazon for loads of money; but otherwise this defining record has probably been more read about than actually heard. You sense that preparing this reissue has been on Emanem boss Martin Davidson’s bucket-list for years and this ultimate Karyōbin comes with a gleaming new mix and a bounty of session photographs. But what makes Karyōbin such an essential, musically urgent listen? Any album that includes Kenny Wheeler, Evan Parker, Derek Bailey, Dave Holland and John Stevens can’t be bad, you’re thinking, but what’s fascinating about Karyōbin is the sense that the musicians are not just improvising the notes and rhythms – the whole idea of what improvised music could be, should be, might (or might not) be, is up for grabs. Over six pieces, the five musicians obstinately reshape and reconstitute the ensemble – Wheeler’s clubbable if fragmenting melody lines forming a brief alliance with Holland’s ping-ponging bass, before the focus shifts to Bailey’s aridly dry guitar pea-shooting notes at Steven’s light, high pitched drum kit. Dig down deep in the DNA, and the heat and spontaneity of jazz clearly plays its part; but these musicians are working with a whole other vocabulary, traces of Webern bouncing into a considered distillation of the lessons of fire music. As regards British improv as a going concern, the game was certainly afoot.