Fifteen months ago, Mark Ronson got a text from his friend George Drakoulias, the man who’d discovered LL Cool J and the Beastie Boys.

It contained just one word: “Barbie?”

Drakoulias had been hired as a music supervisor for the Barbie film and he had an urgent request from writer-director Greta Gerwig.

An early sequence showed Margot Robbie enjoying her perfect day in Barbie Land, hanging out by the pool, surrounded by fellow Barbies and doted on by the perma-tanned Ken.

There was just one problem: The scene culminated with a giant, 60-person dance number… but they hadn’t got a song for it. Could Ronson write one?

“The pressure was crazy because they were going to start dance rehearsals in two weeks and they wanted this big song that could potentially be a hit,” he tells the BBC.

What Drakoulias didn’t know was that Ronson is a huge fan of Gerwig and her co-writer husband Noah Baumbach. After a quick glance at the script, he agreed to help.

“They could have probably said, ‘We’re making a movie about Matchbox cars,’ and I’d have been like, ‘Cool, if you’re doing it, it’s gonna be great’,” he laughs.

With the deadline imminent, he got to work with Andrew Wyatt (with whom he won an Oscar for the A Star Is Born hit Shallow) and together, they turned in a big disco number, full of sweeping string lines and funky bass licks.

Gerwig loved it. It was locked in for the film.

And then Ronson faced an even bigger struggle: Taking the instrumental track to an artist and persuading them to sing on it, without being able to make any changes to the song’s tempo, feel or structure.

“It just had the beat and the strings. There was no melody, no lyrics, nothing. All I’d written was the working title ‘Tastes Like Barbie’ because I thought that sounded kinda cool.”

His first instinct was to send it to Dua Lipa, whose Future Nostalgia album shared many of the same reference points.

On 31 March, 2022, as Dua got ready for a concert in Seattle, Ronson sent her an Instagram DM, inviting her to “co-write and star” on the track.

“Because Dua has such a voracious intellectual curiosity for art, culture, film, everything I just knew she would she would dig it,” he explains.

“She said, ‘Yeah, cool,’ and she ended up coming to New York and we wrote the song together.”

Gerwig was so impressed with the result that she asked Ronson to curate the entire soundtrack… and then to score the film as well.

Her pitch was that Barbie’s story was a parallel to the Bee Gees in the 1970s. Back then, the British trio were the most popular band in the world and Saturday Night Fever was the biggest-selling album of all time.

Then, in 1979 the “Disco sucks” movement culminated in Disco Demolition Night, where a local DJ called on listeners to destroy disco records in a Chicago baseball stadium.

The stunt was ugly, with undertones of racism and homophobia, and the Bee Gees were caught in the crossfire.

“They were interviewed a couple of weeks later and they were like, ‘All we did ever did was just write great pop songs. Why do people hate us so much?’” says Ronson.

“Greta saw a parallel with Barbie in some ways. The Barbie character, all she ever wanted to do was make people happy. But she also represents a lot of things that are problematic and really reviled.”

Unlike previous films he’s worked on, Ronson says Gerwig had a “very specific idea” of how the music would complement the action.

“No offence to the Ghostbusters reboot film, but I remember being one of 11 songs on there that re-interpolated the Ray Parker Jr. theme because there was no directive,” says Ronson.

“But with this it’s hard to tell which came first – the film or the song.”

Audiences can judge for themselves when the film opens on Friday. Until then, Ronson talks us through the soundtrack’s highlights.

Lizzo’s track opens the film, establishing the idyllic, pink-hued world that Barbie inhabits. But the chilled-out vibe is completely at odds with the song’s frantic creation.

“We had two days, and we got nothing on the first one,” says Ronson. “I was like, ‘Maybe it’s not gonna happen’.

“Then she started freestyling and narrating, in a very tongue-in-cheek way, whatever was happening on the screen, no matter how ridiculous, like, ‘Two Barbies, all dolled up and playing chess by the pool’.

“We just started laughing but then we realised: This is musically good, and this is fun, so we ran with it.

“I showed it to Greta and she flipped out. At that point, the song ended halfway through the credits because there’s a Helen Mirren voiceover that comes in. But Greta was like, ‘Tell Lizzo she can keep singing! She can sing at Helen! They can have a dialogue!’”

That idea never made it to celluloid, but it did pave the way for Lizzo to have another musical number later in the film.

“There were two things that were keeping me up at night: What are we doing with Aqua? And how do we possibly have the soundtrack without Nicki Minaj on it?” says Ronson.

These were thorny issues.

Barbie’s creator, Mattel, sued Aqua in the 1990s, saying their smash hit Barbie Girl had brought the doll into disrepute.

A judge later dismissed the case (writing in his opinion that: “The parties are advised to chill”) but Aqua initially said they would not participate in the movie.

Minaj, whose fans are called Barbies or Barbz, was also deemed essential for the soundtrack – but she rejected “a couple of songs that I didn’t love,” she confessed at the LA premiere.

The turning point came when Ronson invited Ice Spice to flip a sample of Barbie Girl.

“She’s the most exciting new thing in rap,” says Ronson. “She’s keeping New York alive.”

Along with her producer, RIOTUSA, she took Aqua singer Lene Nystrøm’s iconic “life in plastic” hook and stapled it into a dark, New Jersey House beat.

“I loved it,” said Minaj, agreeing to the collaboration.

The only problem was fitting the recording around Ronson’s schedule.

“Ice Spice was supposed to come to my studio at 9pm and, you know, I’m an old guy with a brand new baby,” he says.

“I waited till 11pm sharp, then I got into bed – but when I looked at my phone, it said, ‘We’re on the way’.

“I literally was in my pyjamas, but I put my clothes back on, rode my bike back to the studio and showed Ice and Riot the film. And the song started from there.”

Minaj wasn’t the only one who wanted to cover Aqua’s classic.

“Barbie Girl is such an important song to Charli XCX,” says Ronson. “She’s told the story of singing it in a talent show when she was four. And she did a draft of it, but then she wrote the Speed Drive song, and it just elevated the film.

“We loved it so much that we said, ‘Can we keep this?’”

The British star’s contribution is a electrifying jolt of hyperpop that somehow combines elements of Tony Basil’s cheerleader anthem Hey Mickey with Cobrastyle, an underground rap track by Danish band The Teddybears.

But her version of Barbie Girl has subsequently leaked – with producer AG Cook playing it at one of his recent DJ sets.

Sung from the point-of-view of Barbie’s much-maligned boyfriend Ken, this Sam Smith track is a delicious deconstruction of hot, simple himbos.

“No I’m not gay, bro / But I’ve been on that lay-low,” drawls Smith in an uncharacteristically gravelly voice.

“This comes at a point where you really feel you need to feel the freedom of the Kens,” says Ronson.

“Greta showed Sam the scene and they started talking about the feminist mystique and all these very deep texts that I know nothing about. So I just shut my mouth and listened.

“Soon after, Sam sent me a voice note of this incredible melody, literally just singing a capella, and it leapt off the phone.

“It’s so much fun to see artists take some licence, and do things they might not do on their own records because they’re writing in character. Sam’s playing the Kens in the verse, then they go into this yearning Sylvester voice in the chorus and it just explodes.”

…In which Ryan Gosling bares his soul (and his chest) with a show-stopping Broadway number about playing second fiddle.

“I’m just Ken / Anywhere else, I’d be a 10,” he sings, before the song explodes into a Hair-style rocker, with guitars by Slash and Wolfgang Van Halen.

Originally intended for an (unnamed) pop star, Gosling lobbied to sing it himself.

He came straight from the set to Ronson’s studio, with the producer transposing the track to a lower key, to make it easier to sing.

“But each time he sang it, I was like, ‘He sounds killer, l think we can bump it up,’ until we were back in the original key,” he recalls.

“I was over the moon because, at first, I was like, ‘Okay, maybe the song won’t be as good as the demo’ but in the end he exceeded the demo.

“And then when I first saw the film, with him actually acting out the song, I was like, ‘Of course!’ Because he knew that, at some point, he’d be acting out these lyrics, so he was already doing it in the studio.”

Eilish’s song cuts to the heart of Barbie’s predicament: What happens when the world turns against you?

The singer, who’s fought her own battles against public perception, said inspiration hit her “like a tornado” after watching a rough cut of the film.

Within 24 hours, she sent Ronson a text saying, “‘I wrote something today’, with a smiley face, as if it was nothing”, he recalls.

“The next morning, we got this MP3 and it just floored us.

“I was like, ‘How have they summed up the film so well?’ Because by that point. we had Ken’s journey but we didn’t have Barbie’s…

“Greta likes to call it like the glittery pink heart at the centre of the film. And that’s what this song is.”