High off the success of 1984’s Purple Rain – the No 1 film and soundtrack album, which took $220m (£170m) at the global box office – Prince dived into a follow-up, with more power, more control, more whimsy, and more self-indulgence. Feeling invincible, he directed 1986’s Under the Cherry Moon himself. A meandering oddity shot in black and white in France, it was a defiantly uncommercial successor and admirable in its unpredictability, but had little other merit, and disappeared swiftly. The soundtrack, though, is a different story.

It doesn’t even share a title. Parade is one of Prince’s finest musical moments, a crystallisation of an artist at his peak. Other than some French flavour here and there, there’s no indication that it’s married to its film – it gave us Kiss, one of his biggest hits, with an accompanying video that bore no relation whatsoever to Under the Cherry Moon. And now, film and soundtrack seem completely severed. While the album’s cinematic appendage is all but forgotten, a footnote in Prince’s history, the music lives, a key part of Prince’s legacy – and it’s now hard to listen to the mournful closing track, Sometimes It Snows In April, without tearing up over Prince’s own death.

These relationships always start with love and unity – they just sometimes split further down the road. Soundtracks exist to enhance and heighten the on-screen experience, but even if the films fail to find a home in our hearts, the music just might. In recent years, accompanying albums to some films seem more artistically pure then the main event, with clearer vision and entertainment value.

Despite best intentions and tireless work, there are films by great directors that just miss the mark, but their soundtracks brim with love, and a dedicated vision. Cameron Crowe’s We Bought a Zoo was sugary, but the soundtrack, by Sigur Rós’s Jónsi, was an otherworldly delight. Tim Burton’s take on Roald Dahl’s Charlie and the Chocolate Factory was awash in fabulous production design but dramatically askew. Danny Elfman’s score and songs though are a wonder, the album a project in itself. Elfman took Dahl’s original Oompa-Loompa lyrics and brought them to life with kooky magic, harking back to the singer’s own roots as vocalist for his old band Oingo Boingo. So it goes – despite moments of greatness, Quentin Tarantino’s Death Proof was a rare misfire, but its impossibly cool soundtrack really revs your engine.

Likewise, some films of yore get short shrift these days, but still retain credibility thanks to the songs. It’s hard not to think of Saturday Night Fever without instantly hearing those Gibb falsettos in your head. The film was an effective snapshot of a scene, but can hardly be called a classic outside of those confines, whereas its Bee Gees songs are more appreciated by the day. The unfeasibly pretty How Deep is Your Love is constantly embedded on radio playlists, and Saturday Night Fever has endured as an iconic piece of pop culture because of its music.

In the 1990s, soundtracks enjoyed a conceptual moment. Nine Inch Nails’s Trent Reznor, before becoming a score composer himself, produced the compilations for Oliver Stone’s Natural Born Killers and David Lynch’s Lost Highway, and both results seemed like artistic statements in themselves – intricately designed soundscapes that elevated the form. Meanwhile, collections of new music for some less inspired cinematic output appeared: Judgment Night’s rock meets rap collection, featuring the likes of Faith No More teaming up with Boo-Yaa Tribe, was terrific at the time, while superhero film Spawn married metal to electronica, with Metallica’s Kirk Hammett going at it with Orbital, and Henry Rollins bashing heads with Goldie. Both albums are very much products of their time, but they brim with energy and ideas, notable historical documents that are still very much worth a listen on their own terms.

Score-wise, recent orchestral work has also survived less impressive cinematic legacies. Daft Punk’s sublime work on Tron: Legacy lent the film vitality and still sounds fresh, and John Williams’s work on George Lucas’s Star Wars prequels is bold and powerful. The music for these films was lovingly created to heighten our emotions in cinemas, but lives on in our speakers – blast them out on the Sonos Playbase, which is as equally crafted to facilitate true appreciation of the score as it was for the movies themselves, and see if your hairs don’t stand up.

History is riddled with such outliers. Sometimes, in fact, all you need is one big slushy song to dwarf the legacy of its big sister. Boyz II Men’s End of the Road? Written for Eddie Murphy’s long-gone Boomerang. Whitney Houston’s I Will Always Love You, meanwhile, resulted in The Bodyguard being the biggest selling soundtrack album of all time (45m copies and counting). Sometimes, films just die. The songs, though, are played to death, and then some.