Listen out for the harp melody in a scene of cyclists pedalling through the rain – it’s not one of Vangelis’s electronic glissandi but Gail Laughton, an American jazz harpist, from his album Harps Of the Ancient Temples, made in 1978 – a 20th century reimagining of what harp music of the past might have sounded like.

Vangelis's music – an almost symbiotic relationship between sound and picture that creates a synaesthesia-like effect for the viewer.

This was the era of Fourth World music – the phrase coined by trumpeter Jon Hassell for the combination of electronic sounds with traditional African and Indian instruments that he used on albums like Possible Worlds, a collaboration with Brian Eno, in 1980. But while Hassell and Eno created dreamy, often blissful meditations, the Blade Runner soundtrack is tinged with anxiety – a simmering fear of the other that’s mirrored in the orientalist clichés that visually define the city’s sketchy "third" and "fourth" sectors.

Notice how Vangelis uses exotic musical tropes to signal intrigue, decadence and danger, as when Deckard goes in search of the replicant Zhora at the Snake Bar, and we hear a seductive, ambiguously gendered voice – in fact it’s the Greek singer Demis Roussos – singing a sinuous pentatonic melody in deconstructed Arabic, over a menacing synth drone.

I’ve always loved the way that Blade Runner, a film so bleakly, so violently obsessed with the real and the fake, lends itself so well to creative strategies of sampling, looping, hacking and copying. After all, it is itself a masterclass in appropriation and layering, from the doo-wop pastiche "One More Kiss, Dear", created by Vangelis and session singer Don Percival as a replacement for The Ink Spots’ "If I Didn’t Care", to the famous hum in Deckard’s apartment, borrowed from Star Wars.

It’s perhaps not surprising that Blade Runner’s music and dialogue became a go-to source of samples for the UK’s drum 'n' bass and rave producers in the 1990s, with fragmented and reassembled in classic singles such as Dilinja’s “The Angels Fell”. You can hear how Blade Runner’s imagined cityscape resonated with musicians in real cities – London, Bristol, Manchester – for whom this dystopian fantasy could be recuperated into vital new music. In 2008, Zomby’s album Where Were U In '92 samples Roy Batty’s dying speech in homage not only to Blade Runner but also to the club music on which the film was such a key influence.

Meanwhile in Detroit – that paradigmatic post-industrial city – techno producer Kenny Larkin fires up Deckard’s Dream, a neat black box with familiar looking red, white, green and yellow faders. Recently released by a Japanese company called the Black Corporation, Deckard’s Dream is a new synthesizer that, while less than half the size of the Yamaha CS-80, reproduces its signature sounds and action with loving fidelity. This is a high-end replicant, a Nexus-6 job. Who needs the real thing?

This is an abridged version of Sounds of the Future Past, Frances Morgan's talk as part of the BBC Radio 3 series, The Essay: 2019 – The Year of Blade Runner.

Frances Morgan is a writer based in London. She writes about music, film and sound for The Wire, Sight & Sound and others, and is currently researching histories of electronic music at the Royal College of Art and the Science Museum.