Founded by visionary producer Adrian Sherwood and Slits singer Ari Up, aka Munich-born Ariane Daniela Forster, New Age Steppers were a loose collective featuring a rich talent pool: among them, Mark Stewart and Bruce Smith from The Pop Group, reggae crooner Bim Sherman, Aswad bassist George Oban, experimental improviser Steve Beresford, future pop queen Neneh Cherry, drummer Lincoln “Style” Scott and more. Notable for releasing both the first ever single and album on Sherwood’s long-running underground label On-U Sound, the Steppers relished the seemingly infinite new possibilities and fertile tensions opened up by post-punk, blending covers of obscure Jamaican imports with psychedelic dub sonics, free jazz, industrial funk and musique concète collage, mostly cooked up in a cramped dungeon studio below east London’s Berry Street.

Reissued both as individual albums and as a five-disc boxset, this lavishly repackaged retrospective confirms the Steppers, 40 years on, as tireless analogue explorers and forerunners to sci-fi soundscape masters like Burial, Andrew Weatherall and Flying Lotus. Released in January 1981, their self-titled debut still crackles with Ari’s thrillingly untamed vocals, all hard Teutonic consonants and crazy-paving tangents, which sound beautifully incongruous on swooning lovers rock serenades like Sherman’s “Love Forever”. Elsewhere, Stewart’s anguished political sermon “Crazy Dreams And High Ideals” gets lost in Sherwood’s Radiophonic fog of echo, hiss and clank.

The covers-heavy Action Battlefield, also released in 1981, and its 1983 sequel Foundation Steppers nudged the band towards more conventional melody and production. Ari Up effectively took charge, living and recording in Jamaica before bringing tapes back to London for Sherwood to finish. Alongside Ari’s mellow reggae numbers and ramshackle renditions of standards like “Stormy Weather”, a teenage Neneh Cherry makes her studio debut on the sweetly wonky bluebeat doo-wop skank “My Love”. Bim Sherman also lends his velvet croon to several tracks, notably the sublime “Misplaced Love”.

In October 2010, Ari died of breast cancer at the cruelly young age of 48. Posthumously completed by Sherwood and released in 2012, the final Steppers album, Love Forever, is both sombre memorial and refreshing restatement of the band’s progressive manifesto, adding dubstep, trip-hop and bashment elements to the fissile mix. Meanwhile, Ari’s riot grrrl howl on kinetic dub-punk beasts like “My Nerves” and “Musical Terrorist” recall her Slits heyday.

The most welcome and useful disc here is Avant Gardening, a newly compiled retrospective of rare mixes, B-sides and restored offcuts from the early 1980s. Sherwood’s sonic alchemist side is strongly represented, not least on the magnificent title track, a trippy inner-space odyssey of deconstructed dubtronica, wistful melodica and haunted music-hall piano. The sole “new” addition is Ari’s slight but warm-hearted take on Atlantic Starr’s bittersweet break-up ballad “Send For Me”, salvaged from a long-lost 1983 John Peel session.

Four decades later, many of these innocent youthful experiments still radiate more forever-fresh futurism and genre-dissolving ambition than most 21st-century avant-rock artists.