In the strange, silent summer of 2020, an album was quietly released by a renowned soundtrack composer. The making of it had been with him for a long time, since 2014, in fact, when his girlfriend had unexpectedly died. Other things had got in its way, including scores for Ben Wheatley's High Rise, Duncan Jones' Mute and Carol Morley's Out Of Blue. But Clint Mansell remained driven to finish Berlin, to make something solid out of the trauma of grief, to make a fitting memorial to Heather Joy, in all her complexity, in the right way.

I speak to Mansell over Zoom on a bright LA morning. This is one of only two interviews he's done about this record since it came out in late July, after tQ got in touch. He is sitting on a sofa in his nearly-empty flat wearing black-framed glasses, his beard long, silver-speckled and bushy. He's about to move out, but doesn't know where he's going yet: the state of Covid-19 America and the coming elections are unsettling him hugely: "Seriously, I don’t know what I’m going to do. I mean, you can’t ever know what the future holds, but in normal life, you have a certain stability in the present, and now that present instability seems…" He laughs, darkly. "Very unstable!"

Mansell's forty-year career in music has often taken some surprising turns. After his first band, From Eden, in 1981, came Pop Will Eat Itself, grebo punks who moved towards sample-led, electronic industrial rock, which bagged them 11 top 40 hits. Mansell left PWEI in 1996, then was contacted by fledgeling American director Darren Aronofsky, for whom wrote his first soundtrack, the drum-and-bass-fuelled noir masterpiece for 1998's Pi. His subsequent scores have included fantastic, twisted Romanticism (the Grammy-nominated soundtrack to Aronofsky’s Black Swan), spacious, stunning ambient (for Duncan Jones’ Moon) and midnight-shaded, solo piano (for Massy Tadjedin’s Last Night).

And now comes a track-by-track recasting of Lou Reed's 1973 LP about a tragic couple dealing with drug abuse and depression. It's a collaboration with Clint Walsh, a friend, producer and talented guitarist who played in Gnarls Barkley's live band, as well as with David Sylvian, Juliette and the Licks and Bonnie Prince Billy. The Berlin they've made together isn't a copy in style, however: instead, it conjures up the sounds of jangly goth-pop, early '90s synth, and classic singer-songwriter balladry.

This decision has good reason behind it, Mansell, explains: it’s all about Clint letting himself go, and letting Heather in. Speaking generously and with emotion often halting his sentences, he begins by recounting how the 2007 film of Berlin by Julian Schnabel – capturing Lou Reed's live performance of the album in St Ann's Warehouse, Brooklyn, in 2006 – was one of the last films they watched together.

What was the background to you watching Berlin with Heather?

Clint Mansell: Well, Heather struggled, mentally. She had anxiety, mostly, and trauma, that led to her drinking, a bit like the rest of us, really. She had a lot of trouble sleeping – this would be the normal course of events, her struggling through the night, and falling asleep early morning. But one night when we were both awake, I picked up this DVD, and said, 'Shall we watch this?' If you have anxiety, you need something to distract you, and you try and find something that works. That night, this really did.

Do you mind speaking about your relationship?

CM: We were together for three years. We met online through mutual friends. One day she tweeted she'd like to get to know me to see how my mind works [laughs]. I knew she was a big reader, very literature-oriented, so I invited her to a barbecue of a friend who'd just publish a book. She replied: "you just melted my little black heart of coal." I have some of her ashes in a little black heart.

It just went from there. We didn't have a relationship like the one in Berlin, I hesitate to say, but we butted heads because we were both opinionated! We also both loved the Velvets and Lou Reed. I first heard of him in the music papers, but then I was at the mercy of record shops who might and might not have his records, then I wouldn't have enough money to get them anyway. The first music of his I actually heard was at this great club in Dudley called JBs. It was 'Venus In Furs'. I couldn't believe what I was hearing.

Heather Joy's photograph of the Berlin DVD the couple watched

I loved how he made these huge statements like Metal Machine Music off the back of Transformer and Berlin. I remember hearing New Sensations when it came out, when I was sharing a flat with Miles Hunt, how Lou'd sing about getting a burger and a coke and made it sound like poetry. I bet he was hard work [laughs] but he was always surprising and challenging, all the things you aspire to you in yourself.

As for Heather, she was from New York and loved all things New York. Lou Reed was so New York. So there was something comforting in watching the live performance of Berlin together, even though outwardly, it's a very tough, dark stark record. Anthony [Anohni] was also singing with Lou that night, who I'd worked with on The Fountain, so there were all these warm connections.

Did Heather enjoy it?

CM: Yeah, she loved it. She posted a picture of the DVD cover on her Instagram, saying how much she enjoyed it at 3am. It's funny, I've heard some people saying that they didn't get Berlin when it came out, but it came into their lives in a big way at another time or another place, and that's how it happened for us. I mean, one of the things I do like about the internet is how it has flattened time. If a record is forty years old, it doesn't really feel old. When you're ready to hear it, it's there for you.

Anyway, I consequently forgot about that evening to some degree. It was a great evening, but, you know, life goes on. Then when Heather got sick… and ultimately died…[for the next few minutes, Mansell takes his time, pausing often to hold back his emotions]. It was really traumatic.

What happened?

CM: She was in hospital for five weeks. She had pneumonia which caused her organs to shut down. Then she was induced into a coma for twelve days to get the fluid out of her lungs. She got through that, but she got a secondary infection later, and her lungs were so damaged, she couldn't fight it. The ironic thing was that the doctors thought she'd got the pneumonia from inhaling vomit while throwing up while going through alcohol withdrawal. She had been trying so hard to get better. It was doubly cruel.

I did grief counselling and therapy just to try to… you know… I don't know… it was sheer panic, really. Trying to take on board this information that somebody had gone.

Heather Joy's photograph of a washing line at Greenpoint, her favourite of all her pictures

Did the grief counsellor help you?

CM: They said, "You're a musician, you should write music to try to channel this." And I got that, but nothing made any real sense. I couldn't write something that went, "Oh, I'm sad." Oh yeah, no shit! It didn't seem there was any relevance to that. But weirdly, just after Heather died, I was about to start High Rise with Ben Wheatley, who I'd just met and talked to for the first time a few months before, all excited, because I loved Ben, and loved JG Ballard. I called Ben after she died and said, I'm not going to be able to do this, and he understood. But a few weeks later, I was over in the UK to see my parents for Christmas, so I saw if Ben wanted to meet up for a drink in London. Eight pints later, he said, "Why don't we wait for you?" [Holds back tears] I mean, it was the most beautiful thing. You know what this industry is like. Nobody's got time for anyone.

It was absolutely what I needed, because the last thing you want to be when you're in that state is left to your own devices. At the same time, it's hard to commit to anything and knuckle down. So I started High-Rise in late January, and the reality I was effectively channelling what I was going through into that. I also made another film [Man Down, directed by Dito Montiel], which I'd said I couldn't, but then I found out he'd directed another film Heather loved, A Guide To Recognising Saints, and I was like, "What the fuck?! I have to do this." So everything was being channelled that way. In the last few years, I've also worked on [Duncan Jones'] Mute and [Ben Wheatley's] Rebecca [out on Netflix on October 21], which both deal with loss. In Mute, he's trying to find her. He doesn't know what's happened with her. He's on the brink of hope and hopelessness.

When did the idea of Berlin come to you?

CM: Maybe later in 2016. I remembered us seeing Berlin together, and something about doing that album in a different way added up. I'd loved Pussy Galore covering Exile on Main Street, and I knew Beck was doing similar things [covering albums for his Record Club Project]. This precedent of rock & roll expressing itself in that way spoke to me. Also, this was a piece of music I had shared with Heather, and suddenly it could be something we could share again.

Did Berlin's bleakness worry you, given what you'd been through?

CM: A bit. The record's depressing enough as it is! [laughs] That's when I started talking to Clint [Walsh]. We were on tour when Heather first got sick, as he was in my live band [performing the soundtracks], so he'd been around for all of it. He was also having tough life experiences of his own, of a different nature, so we were both in not great places. We started hanging out and brainstorming it, and I realised rather than me going 'Poor old me' – rather than it becoming about my suffering, for the want of a better, less overblown word – the album should be more about Heather and her world and what she was and the things she loved. To take me out of the equation.

A lot of the songs are in very different styles from the original album.

CM: We took T-Rex, The Cure, Oasis, stuff that she loved, Springsteen, Elliott Smith, and gave it a sprinkle of our idea of New York. There's such a narrative going on in Berlin too, isn't there? It's more like a musical or a stage show – it's of the time of The Rocky Horror Picture Show or Cabaret, and Berlin has that feeling in its seeds. I mean, ‘Caroline Says’ is the middle of the show to me. Thinking of what we were doing in those terms helped remove my gloominess a bit.

The turning point was ‘Lady Day’. Clint came round to my house with a rough demo which blew me away. It was nothing I'd done, but it had this energy and life that lifted me out of where I was. Before that, I was stuck in a bit of a grief groove. Clint kicked it out with this vibrancy which retained what Lou Reed did, and gave it this hopefulness. That hopefulness was transformative for me. It opened up the prospects of the record.

Did you enjoy collaborating this way? I assume normal working life for you is very solitary, in a studio with your gear and a massive screen.

CM: But it's usually very collaborative with a director, even though I write all the music. For me, the best collaborations are the ones where you end up a) where you never would have imagined getting to, or b) where you could have never got to on your own. With Ben, Darren, Duncan and Carol, those are the best experiences. You come together, talk, create the soil for it, it suddenly starts working, and it grows, and you follow it. It's a magical thing. That's what happened with Berlin, although I should say that Clint did so much. He's such a brilliant producer, making all these disparate arrangements fit together. He also pushed me so much, and convinced me to sing for the first time in 25 years.

What was that like?

CM: I mean, I hate my fucking voice, but I found that when Clint and I sang together, I really liked it. It made me think of Alice In Chains when Layne Staley and Jerry [Cantrell]'s voices coming together in these harmonies – they're not sweet, they just get to this place that feels good. There's something very primal about singing, and I liked that. It's also letting down inhibitions, isn't it? It's exposing yourself to what you're feeling, which is the hardest part of grief. Singing brings you a little closer to that because you're letting down barriers. It's not a natural thing for most people to do, even for proper singers. They don't just do it in the supermarket. They've got to get in the zone.

You started making Berlin after you and Walsh worked together on the soundtrack for the Emmy-winning Black Mirror episode ‘San Junipero’, which came out in late 2016. You finished Berlin earlier this year. Did it take a while because of your film commitments, or because of the intensity of making such a personal project?

CM: Both. We had three months where we didn't speak! [laughs]. We're similar people in that we struggle with our communication sometimes, although we hadn't really fallen out. I was just so intense for both of us as a project. But then we bumped into each other at a gig and got back to it. We got it mixed just before lockdown. And it was lockdown that brought the whole thing home to me.

In what ways?

CM: We're somewhat used to the way the world is now, even though we don't know what's going to happen, but things felt so dystopian back in March when we had that sudden shift. Around then, I played the whole album back – and I don't want to sound too grandiose – but I heard it from the place I was at at that moment. There was a vulnerability about it that spoke to that moment.

That's when I knew I wanted to put it out, but I didn't want to make a big release of it. In many ways, just doing the record was enough. So I spoke to Reg at Invada [Geoff Barrow's independent label in Bristol] and it came out quietly, and I hoped that people might just come across it. I was chuffed when The Quietus did. This is only one of two interviews I'm doing about it. That's enough. It makes it more special.

And I have to ask, finally: what do you think Heather would have thought of it?

CM: [Smiles, and takes his time to answer] I kept thinking of that all the way through. Her favourite word was no, so I imagine that she'd probably be very critical! [laughs] She was not shy with her opinions, so she'd have plenty to say about it. I loved that about her.

But I hope she'd like it. [pauses for a moment] I think she probably would, to be honest. She'd be touched. But I hope others realise that it's an album not just about grief and loss that are unique to me, just as Heather's struggles were not unique to her. There's a universality to the feelings in this record. They feel like lonely experiences when you're having them, but it's so easy to forget there's a crowded waiting room out there. I hope there's hope in that, and hope in there, somewhere.

Berlin is out now on Invada