Batten down the hatches, this is a big one. The meat of March On is a 32-minute group improv that is a Moby Dick of a song, starting deep and going, well, deeper. Recorded after last year's March sessions, the plan was to edit it, using elements as segues on the original album.

Instead, we now have the whole heaving maelstrom, as the various double trios buck and yaw in call and response to each other's pleas, pokes and provocations. Calm follows tumult – and a blazing poise unites it all.

All these musicians are of course richly steeped in improv idioms, but each is a talented composer in their own right. So, there's a strong sense of composition even mid-improv: it's free but not anarchic, in the moment but expressive of years of experience. This is a collective will at work and play, much as the inspiration for the original March album was the collective outpouring found in protest and marching songs. In an elegant touch, the improv is gloved between two duets shaped by the different voiced guitarists, Halvorson and Seabrook. The opening ‘Smoke’ has a music box patina as the pair jangle harmoniously while Seabrook evokes Derek Bailey on the aptly titled ‘Docile Fury’. ‘Silhouettes’ finds the guitarists leading us out to, well, where does this lineup go after this?