They were promoting their new album Double Fantasy, but the two-hour conversation was wide ranging.
Though the interviewers had been warned "no Beatles questions", Lennon and Ono were thrillingly open. That day, Annie Leibovitz also shot the famous portrait of a naked Lennon wrapped around Ono.
The interview is similarly naked. The two, particularly Lennon, riff on love, their relationship, creativity, life after the Beatles, raising their toddler son, writing songs in bed and much more.
At the age of 40, Lennon sounds like someone who has found real clarity.
"I feel like nothing happened before today," said Lennon.
In John Lennon: The Last Interview, Steven Soderbergh turns those surviving tapes into a documentary that does as much to demystify Lennon and Ono as Get Back did to the Beatles.
The film debuted on Saturday at the Cannes Film Festival.
"I was just so compelled by their generosity of spirit throughout the conversation," Soderbergh explained.
"It's like the world took place in one day, in this apartment."
Making it posed an acute problem.
Soderbergh was resolved to let the audio play. He could find ways to visualise much of the film, but that still left a large gap where the conversation grows more philosophical.
"I worked on everything that could be solved except that for as long as I could," Soderbergh says.
"Then there was the inevitable moment of: okay, but really what are we going to do? We just started playing and ran out of time and money. That's where the Meta piece came in."
Soderbergh accepted an offer to use Meta's artificial intelligence software to conjure imagery for those sections, which make up about 10 per cent of the film.
When Soderbergh let the news out earlier this year, it prompted an uproar. One of America's leading filmmakers was using AI? In a film about a Beatle, no less?
The AI parts are fairly banal and don't differ greatly from special effects.
But Soderbergh put himself at the forefront of an industry-wide debate about the uses of AI in movie making.
For Soderbergh, who has made movies on iPhones, it's a conversation he's eager to have.
"Transparency is so important (in) that the world outside of the creative context, we're not aware of the extent that this is being used and used to manipulate us. We don't know because they're not telling. We find out after, by accident, by some whistle blower. I'm like my own whistle blower," he said.
"I understand why people have an emotional response to this subject.
"You don't say yes to Meta offering you these tools and offering to finish the film and not know you're going to come in for some heat. That was part of the deal," he said.
He decided AI was justified in some circumstances.
"I've determined my rule is: It has to be necessary. Is it the only way to accomplish what I want to see? Is it truly the best way to do it? That's the real question. You're going to see a lot of people doing stuff with AI that fail those two challenges," he said.
"Each creative person is going to have their own prism and be affected by it in different ways. Our inherent desire to have a simple template for how this is to be approached is part of the problem. I don't think that's possible. I don't think there's a one-size fits all."
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