Among the most important and influential progressive rock bands of the late '60s and early '70s, Soft Machine initially featured a line-up of Robert Wyatt (drums, vocals), Kevin Ayers (bass, guitar, vocals), Daevid Allen (guitar) and Mike Ratledge (organ). Emerging from the UK (Canterbury) underground in 1967, they featured prominently at epoch-making London venues such as the UFO Club and Middle Earth to establish a powerful reputation over the next decade with a series of accomplished albums and some innovative concert performances; notably in the UK and France. After two albums for ABC/Probe, they signed to CBS with a line-up consisting of Wyatt, Ratledge, saxophonist Elton Dean and bassist Hugh Hopper, releasing this, their most successful long player, in 1970. Marking the beginning of their journey away from their psychedelic roots and into jazz and contemporary electronic music, it is unconventional to an extreme, consisting of four stunning side-long compositions, and is universally regarded as not just their best record but one of the best progressive rock albums ever recorded; one that pushed the boundaries of genre without being pretentious.