From the first whispers of whistling wind, driving basslines and sludgy, slowed breakbeats, the sound of Massive Attack’s 1991 debut is unmistakably theirs. Rooted in the musical culture of Bristol, England, at the turn of the 20th century’s final decade, Blue Lines absorbs the port city’s soundsystem vibrations, industrial grit and post-punk harshness to produce nine tracks of unsettling nocturnal introspection. Starting out as DJ and MC collective The Wild Bunch, Robert Del Naja, Andrew Vowles, Grant “Daddy G” Marshall and Adrian “Tricky” Thaws began turning their hand to production in the late ’80s, thanks to a collaboration with local singer Neneh Cherry on her 1989 single “Manchild”. Encouraged by Cherry and her partner, producer Cameron McVey, the quartet soon adopted the moniker Massive Attack and holed up in one of Cherry’s spare rooms to begin work on what would become Blue Lines. Inspired by the reggae music of the Caribbean diaspora in Bristol as much as by nascent UK rap pioneered by artists like Rodney P and the dub-punk of local heroes The Pop Group, Massive Attack forged a record of remarkable clarity, clothed in the paranoid fug of weed smoke. Opener “Safe From Harm” sets the tone, pairing Shara Nelson’s soulful vocals with record-scratches and a thundering rhythm section, while De Naja delivers a typically anxious hook: “I was looking back to see if you were looking back at me to see me looking back at you.” This tension between unease and harmony continues throughout, simmering in the jazz shuffle of the title track as Tricky drawls menacingly, or weaving through the dub bass and counterpoint of singer Horace Andy’s soaring falsetto on “Five Man Army”. Ultimately, it is on the group’s most well-known track, “Unfinished Sympathy”, that they reach their apotheosis. Pairing luscious string orchestrations with eerie vocal samples and Nelson’s yearning vocal lamenting an unrequited love, Massive Attack create five minutes of soul music that stirs as much as it soothes. The group would go on to be labelled innovators of a new laid-back genre called “trip-hop”, spawning dozens of imitators and hundreds of chill-out playlists. Yet, there is nothing relaxed about Blue Lines: Amid its euphoric melodies is an ominous vocal, and between its groove there is a bassline breaking almost to distortion. On this pioneering debut there is always a reason to look back over your shoulder.