If their debut was the psychedelic origin point and Third was where they finally soldered their jazz-rock tendencies into a permanent place in their sound, this frantic transitional record is a clear difference-splitter — and a charmingly bewildering one at that. Reconvening after songwriter Kevin Ayers left post-debut and bringing drummer/singer Robert Wyatt into the forefront, Volume Two is less a scramble to compensate for a personnel change and more a moment of a band hitting on the realization that they’ve got new elements to play with. Soft Machine click immediately as a trio-plus; Wyatt’s rhythmic restlessness behind the kit and his delicate warmth as a singer are complemented well by Hugh Hopper’s joyously wonky rhythm-complementing fuzz bass and guitar, while Mike Ratledge’s keyboards hit like Ahmad Jamal choosing violence. (Check out Ayers farewell “As Long as He Lies Perfectly Still” for all of these elements at their utmost.) Lyrical themes run a bit absurdist and irreverent — everything from the A-B-Cs (frontwards and backwards) to a self-effacing examination of white privilege (“Hulloder”) to a thank-you note to tourmates the Jimi Hendrix Experience (“Have You Ever Bean Grean?”) that sounds like sunshine pop unexpectedly undergoing controlled demolition. But it all flows together both in Side 1’s “Rivmic Melodies” suite and on the flip’s quick-cutting “Esther’s Nose Job,” mostly-instrumental barrages of short-but-lively little pieces that cohere as rare realizations of both prog and jazz-rock’s potential for lighthearted joy.