From its opening shot, Trainspotting is a movie in motion. As sneakers hit the sidewalk of Princes Street in Edinburgh, Scotland, we hear the raucous drumbeat of Iggy Pop's 1977 barnstormer "Lust For Life." Renton—played by Ewan McGregor—and Spud—by Ewen Bremner—sprint away from two security guards, their shoplifting spoils flying out of their pockets. 

"Choose life," Renton's narration begins, introducing an instantly classic monologue about the emptiness of middle-class aspirations. The action then zips to a soccer match that introduces Renton's ragtag mates: Spud, Sick Boy (Jonny Lee Miller), Begbie (Robert Carlyle) and Tommy (Kevin McKidd). The scene is all propulsion and attitude, with Iggy Pop dropping the match on the trail of fuel. In just 60 exhilarating seconds, Trainspotting tells us precisely what it's going to be.

Trainspotting burst into U.K. cinemas in February 1996, followed immediately by a debate on whether its fizzing depiction of junkie life glorified drug use. Audiences staggered out, scandalized and delighted in equal measure by "The Worst Toilet In Scotland," Spud's soiled sheets and a ceiling-crawling baby. By the time it opened in the US in May, the movie was already a critical and box office hit at home. Its credentials were undeniable, including a compelling young cast led by newcomer McGregor, a visually daring director in Danny Boyle and a script adapted from Irvine Welsh's cult book of the same name. 

In a year dominated by slick Hollywood blockbusters like Independence Day, Twister and Mission: Impossible, Trainspotting was the scrappy, no-kids-allowed outsider that could. One of the movie's most significant talking points, and a key reason for its enduring legacy, was its use of "needle drops" in lieu of a traditional composerly film score. The soundtrack reaches back to the '70s and '80s, while also showcasing of-the-moment Britpop and dance music. The music of Trainspotting endures because it's intrinsic to the movie, with each song meant to elevate a particular scene or moment. 

Read: How 1995 Became The Year Dance Music Albums Came Of Age

Welsh's 1993 novel frames Renton's misadventures as a heroin addict against the dismal backdrop of Leith, just north of Edinburgh's city center. Trainspotting was first adapted as a stage play, with Ewen Bremner (perfectly cast as Spud in the movie) playing Renton. Before long, the movie offers rolled in. "There was loads of interest," Welsh told Vice in 2016. "Everybody seemed to want to make a film of Trainspotting."

Most directors wanted to ground the adaptation in social realism, but Welsh knew Trainspotting needed a wilder take. In 1994, a promising young director called Danny Boyle had made his feature debut with the pitch-black comedy Shallow Grave, starring Ewan McGregor. Impressed by the movie's visual flair, Welsh gave Boyle the keys to Trainspotting. 

The making of the movie was a thrill for all involved. Fresh from writing Shallow Grave, screenwriter John Hodge relished the opportunity to adapt Welsh's book for the screen. (Hodge was nominated for Best Adapted Screenplay at the 1997 Academy Awards - the movie's only Oscar nod.) Before filming, Boyle sent his actors to spend time with Calton Athletic, a real-life recovery group for addicts. The shoot began in June 1995 and lasted 35 days (a step up from the 30 allocated for Shallow Grave), with Glasgow mostly standing in for Edinburgh. 

Alongside cinematographer Brian Tufano, Boyle brought a bold, kinetic style to every shot. "We'd set out to make as pleasurable a film as possible about subject matter that is almost unwatchable," Boyle told HiBrow in 2018. 

While Shallow Grave gave an early glimpse of Boyle's tastes, including his fondness for electronic duo Leftfield, the music in Trainspotting demanded a bigger role. Welsh's book is peppered with references to The Smiths, Iggy Pop, Lou Reed and David Bowie, so the call went out to a select list of musical icons. Bowie was a no, but others who'd loved the novel happily offered up their music to the project. 

Welsh and Boyle were both clued-in to acid house and rave culture (represented on the soundtrack by the likes of Underworld, Leftfield and John Digweed and Nick Muir's Bedrock project), but it was the director's idea to bring in the likes of Blur and Pulp. That decision was a "masterstroke", Welsh told Vice, because "Britpop was kind of the last strand of British youth culture, and it helped position the film as being the last movie of British youth culture."

Several of the best scenes in Trainspotting are soundtracked by songs made before 1990. Following "Lust For Life", the sleazy strut of Iggy Pop's 1977 track "Nightclubbing" lurks behind a sequence of Renton's relapse into heroin. (Both songs were co-written by David Bowie, giving him an honorary spot on the soundtrack.) New Order's 1981 song "Temptation" is a motif for Renton's taboo relationship with high schooler Diane (Kelly Macdonald in her first film role), while Heaven 17's 1983 pop hit "Temptation" plays at the club where they first meet. 

Lou Reed's "Perfect Day" lands the hardest punch. In a dazzling sequence, Renton visits his dealer Mother Superior (Peter Mullan) for a hit of heroin. As Renton's body sinks almost romantically into the floor, we hear Lou Reed softly singing about a perfect day drinking sangria in the park. The romance ends there. Knowing an overdose on sight, Mother Superior drags his sort-of friend to the street, then heaves him into a taxi, tucking the fare in his shirt pocket. (In a brilliant small detail, we see an ambulance rush past, headed for someone else.) 

"Perfect Day" keeps on at its languid pace as Renton is ejected at the hospital, hauled onto a stretcher and revived by a nurse with a needle to his arm. "You're going to reap just what you sow," Lou Reed sings as Renton gasps wildly for air. 

Boyle pushed for Britpop on the soundtrack, but he didn't want obvious hits. Britpop, a genre coined in the '90s to describe a new wave of British bands influenced by everything from the Beatles to the late '80s "Madchester" scene, was at its peak during the Trainspotting shoot in the summer of 1995. Pulp had just released the Britpop anthem "Common People," Elastica and Supergrass were flying high from their debut albums, and genre superstars Oasis and Blur were locked in a media-fueled battle for chart supremacy. 

In the heat of all that hype, Boyle reached back to 1991 and took "Sing" from Blur's debut album, Leisure. The song's stirring piano melody picks up after the "Nightclubbing" sequence, as Renton and his fellow addicts hit a harrowing rock bottom. Later, when Begbie busts in on Renton's new life in London, Pulp's "Mile End" underlines the mood of big city ennui. Along with contributions from Elastica and Blur frontman Damon Albarn, Trainspotting draws on just enough Britpop to keep its cool. 

If Trainspotting has a signature song, it's Underworld's "Born Slippy .NUXX". The duo of Rick Smith and Karl Hyde already had three albums behind them when Boyle reached out to use their 1995 B-side in his movie's climax. The duo was wary—as Smith later put it to Noisey, their music was often sought out to accompany "a scene of mayhem"—but Boyle convinced them with a snippet of the film. Underworld also contributed the propulsive "Dark & Long" to the indelible scene of Renton detoxing inside his childhood bedroom. After Trainspotting, "Born Slippy .NUXX" became the defining song of Underworld's career and a constant euphoric peak in their live sets. 

Just as Trainspotting caught the Britpop zeitgeist, it also immortalized a high point for dance music. A rush of trailblazing dance albums came out in 1995, including Leftfield's Leftism, The Chemical Brothers' Exit Planet Dust and Goldie's Timeless. In a time of rave culture colliding with chart hits, the movie finds room for both the dark electronics of Leftfield's "A Final Hit" and the goofy Eurodance of Ice MC's "Think About The Way". 

In one scene, Renton sits grinning between the speakers at a London nightclub that's going off to Bedrock and KYO's 1993 classic "For What You Dream Of." "Diane was right," he narrates, recalling a conversation from before he left Edinburgh. "The world is changing, music is changing, drugs are changing, even men and women are changing." For the briefest moment, we see the thrill of '90s dance music as it really was. 

The Trainspotting soundtrack album hit shelves in July of 1996. The cover played on the movie's iconic poster design, framing the characters in vivid orange. The soundtrack sold so well that a second volume followed in 1997, featuring other songs from the movie and a few that missed the cut. (The same year, the hugely popular Romeo + Juliet soundtrack also inspired a "Vol. 2.") 

Boyle continued to use music as a key character in his movies, following up Trainspotting with the madcap Americana of A Life Less Ordinary and the pop-meets-electronica of The Beach. After 20 years, Boyle got the gang back together for 2017's T2 Trainspotting. In contrast to the original's wall-to-wall needle drops, the sequel weaved a score by Underworld's Rick Smith around songs by High Contrast, Wolf Alice and Young Fathers. 

Many impressive, star-studded soundtracks followed in the wake of Trainspotting. What makes this one rare, though, is how deeply its unholy union of rock, Britpop and dance music belongs to the movie. Remove any needle drop from a scene in Trainspotting, however fleeting, and it'd lose something vital—that's how you know it's built to last.

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