The luxury box set market is like a microcosm of capitalism itself. It needs to keep on expanding, exponentially in order to survive. Each passing year, the same desirable pieces of recorded music must be repackaged as bigger and better releases than ever before. That LP you’ve already got three ‘definitive’ copies of; wouldn’t you actually like it as a luxury box set but this time with the pre-demo dictaphone ‘sketches’ in 5:1 surround sound on emerald green splatter vinyl with four limited edition beer mats? If you feel attacked by this, please don’t. Now that the memory of daily infusions of peach schnapps, Capstan Full Strength and granulated amphetamine sulphate is so faint it barely feels like it even happened, fetishising unnecessary luxury reissues and box sets is genuinely one of my worst habits. But just because most of these releases are both pointless and pernicious from the consumer’s POV, that’s not to say that the record companies don’t actually sometimes get it right.

Last year UMC issued the fabulous if slightly exhausting trip through imperial-period Tangerine Dream’s archive in the shape of In Search Of Hades. This 16 CD and two DVD cache of the band’s glorious 1974 - 1978 Phaedra, Ricochet and Rubycon phase really hit the mark. On first glance, this year’s follow up box set - Pilots Of Purple Twilight - The Virgin Recordings 1980 – 1983 doesn’t exactly scream ‘Keeper!’ in the same way however. Somebody should have had a word with somebody else about the poetry of the words “purple” and “twilight” for starters. And to what extent do we even need to worry ourselves about what Edgar Froese, Johannes Schmoelling and Chris Franke were up to at the start of the 80s? For example, the five tracks Tangerine Dream donated to the soundtrack of the now all but forgotten about Tom Cruise “teen sex comedy” Risky Business don’t even warrant their own disc. Instead these five songs are an addendum at the back end of the Hyperborea (1983) CD.

No, the main reason for my excitement about this box set is because it marks the first official release of the soundtrack to Michael Mann’s fizzing, transcendental and bewildering occult Nazi horror movie The Keep (1983). To say that this album has been fetishised by fans of electronische stoner oscillations is something of an understatement. To me it’s one of those rarified cult LPs that has been discussed so much over the last four decades by hashish enthusiasts that it has ended up with its own unbreakable urban myth. I distinctly remember spending a lot of time sitting around in various sepia-tinted, shredded Rizla adorned flats in the 1980s and 1990s waiting for various people carrying various things to turn up that the conversation would always turn to Pink Floyd (“There’s a factory in Germany knocking out copies of Dark Side Of The Moon 24/7 and they still can’t meet the demand”); Aphrodite’s Child (“A friend of a friend got burgled and they cleaned out his entire flat including his table, his chairs, his cooker and his fridge and all they left behind was his copy of 666 - snide behaviour”); and Brain Ticket (“If you listen to Cotton Wood Hill on acid you’ll go permanently insane”).

According to the same community of herbalists, The Keep was released on vinyl in 1984 but then withdrawn due to nefarious skullduggery. A bunch of fans, Mandela effect or not, ‘remember’ seeing it in a record shop but by the time they’d been home to pool their resources and returned, all copies had been withdrawn and destroyed. Far out man. The full story of this soundtrack’s 37-year official journey to your ears is incredibly long but it has been recorded faithfully online by a TD megafan, should you want to know more. But suffice to say, the fact that there have been at least 21 bootlegs (none of which got it exactly right) should speak to it’s totemic power.

I can’t hazard a guess as to what kind of frame of mind Michael Mann and his cast were in during filming but everything about The Keep is berserk. Any sense, subtlety or softness has been sand-blasted away from the surface until only bombast, ghostliness and torrid ghastliness remain. Scott Glenn’s character Glaeken Trismegestus looks more otherworldly before he is eventually transformed with prosthetics and contact lenses, while Ian McKellan looks like he actually believes he is an ailing Jewish scientist rescued from a concentration camp in order to help battle an ancient entity called Molasar so that it will stop slaughtering Nazis in a remote Romanian mountain pass during Operation Barbarossa. This is a film that looks at its watch, sees it’s 3am and instead of shame-facedly calling for an Uber, settles in for the long haul, announcing loudly, “Anyway, enough about you, let’s talk about me.” And the soundtrack does little to buck this trend.

This music - as it was originally supposed to be released by Virgin in 1983 but given a new stereo mix by Ben Wiseman - isn’t comprehensive by any stretch of the imagination. The opening theme that accompanies Capt. Klaus Woermann’s Wehrmacht unit as their jeeps thunder along Carpathian mountain roads is sadly missing. This section of music sounds more like Fuck Buttons than Tangerine Dream with its circular drum pattern compressed to the point of tachycardia, glowering with insectile LFO pressure but it sounds naggingly familiar for another reason: Mann was obsessed with the David Byrne and Brian Eno album, My Life In The Bush Of Ghosts; which led to Tangerine Dream recording this incredibly ‘accurate’ cover of ‘Mea Culpa’. Was it copyright wrangling that kept this banging version off the official soundtrack? It looks like we’ll never know.

Instead this CD opens with the altogether more glassily chill, synthetic and crystalline reading of the Thomas Tallis 16th Century hymn ‘Puer Natus Est Nobis (Gloria)’, clouded in airhanger reverb and vododered choral backing. It initially sounds familiar… perhaps it’s calling to mind Paul Chapman’s boy soprano performance on ‘Misere’ - Michael Nyman’s outstanding and funereal centrepiece track from The Cook, The Thief, His Wife And Her Lover - or maybe not. The truth is simultaneously more mundane and more strange.

Principle filming on The Keep ended on December 24, 1982, and on Boxing Day, Michael Mann, who was spending his break in the UK, kicked back by watching the television premiere of the Raymond Briggs animation The Snowman - and was blown away by it. After failing to secure the assistance of Howard Blake - he phoned the composer in a state of animation asking if he would rework the "snowman song" - he enlisted Tangerine Dream to cover ‘Walking In The Air’. Their version graced the two hour long rough cut of the film no less than three times, including a seven minute version over the closing section of the film and the titles. But at some point between then and the film’s premiere all but the last of these sections were consigned to the cutting room floor and, not even the last segment made it to the soundtrack. Now the spectral influence of The Snowman remains merely as a vibe haunting the track ‘Gloria’, which is still enough to give the listener the sense that they are rocketing up seven miles high and then thundering across the snow-blasted skies of Greater London.

Though there is a very lovely indeed 12”x12” hardback book with this boxset written by TD guru Wouter Bessels, the information contained on The Keep is scant. Because the narrative of the film’s production is so complicated, it’s difficult to recount in any kind of concise way, I guess. Which is probably why he neglects to mention that at one point Laurie Anderson was drafted in to mix this music and she in turn influenced Scott Glenn’s distinctively robotic speaking style in the film. Again, for this, and lots of other bits of The Keep trivia, I’m indebted to Kit Rae’s scholarship on the subject.

To be fair, Tangerine Dream were not fans of the ‘pure’ soundtrack - to them such a commission was simply an excuse to record a new album. They’d take musical cues and themes from the film and expand them, turning sketches into full-blown songs. But still, what remains here are the true highs of Tangerine Dream in the early 1980s with few of the lows - and for that I’m willing to be relatively sanguine about Froese’s occasional bout of guitar soloing. Closest in style to the missing Eno and Byrne cover is ‘Canzone’ whose yawning envelopes quickly fill up with a horrific skree of noise and the phasing of synthetic string scrapes, all of which are merely a prelude to Schmoelling’s experiments with orchestral sampling, while Franke’s early use of sampled drum loops make the pitch bent fanfare of ‘Ancient Powerplant’ all the more buoyant, taking the next step on from Harmonia’s primitive but melodic drum machine experiments. Also there is the baroque, Wendy Carlos-style fugue of ‘Arx Allemand’; and ‘The Challenger’s Arrival’ which sounds like a dazzling mashup of Jan Hammer’s ‘Crockett’s Theme’ and Gary Numan’s ‘Films’. What’s not to like really?

(Elsewhere on the box set Hyperborea (1983) is a fine album as these things go, as is their cold war nuclear panic LP Exit (1981) and Logos is the best of the live sets but if you’ve got this far then I’m guessing you probably already know that.)

Pilots Of Purple Twilight is out now