was murdered on Dec. 8, 1980 — but now a final, Lennon-penned Beatles song, “Now and Then,” provides a glimpse of what could have been.

“I think this the closest we'll get to that,” says

(son of legendary late Beatles producer

), who co-produced “Now and Then” with Paul McCartney. “This is the last situation where each member of the band is doing something on a track. This is the last time that all four of them will play on anything. And it sounds like the Beatles are now, as opposed to us trying to create some young thing like ‘I Saw Her Standing There’ or ‘Help!’ or whatever. And this whole project stems from Paul just wanting to work with his friend John again. I think that’s beautiful, in a way.”

“Now and Then” began as a sparse vocals-and-piano demo, recorded by Lennon in the late ’70s at his home at New York’s Dakota Building. It was first heard by McCartney and the two other surviving Beatles at the time, George Harrison and Ringo Starr, in 1994, when Lennon’s widow, Yoko Ono, gave them two cassettes — one with Lennon’s home recordings of “Free as a Bird” and “Real Love,” and a second labeled “For Paul” containing “Now and Then.”

But while the two former songs were eventually completed with producer Jeff Lynne and released as part of The Beatles Anthology series, the technology didn’t exist in the ’90s to effectively separate Lennon’s vocal from the piano and background noise on the “Now and Then” demo. So, the frustrated McCartney, Starr, and Harrison (who died of cancer in 2001) put the track aside. And, as McCartney says in a new Oliver Murray-directed short film about the song, it “just kind of languished in a cupboard” for nearly 30 years.

Martin, however, tells Yahoo Entertainment that he didn’t actually know “Now and Then” existed until last year. And he confesses that when McCartney — newly inspired by the use of WingNut Films MAL audio technology to isolate, or “de-mix,” the Beatles’ instruments and vocals for Peter Jackson’s 2021 docuseries Get Back — approached him about finally completing the song, he was daunted. “I was nervous about hearing it. Because if I didn’t like it, what am I going to say?” Martin chuckles. “It is all very well hearing it, but I’ve got Paul McCartney playing it to me, and he’s already been secretly working on it. But I just listened and thought, ‘Well, actually, this is really good.’ It’s a really great tune — and it means something. And what more can you want?”

Martin says there are layers of meaning to “Now and Then,” a more bittersweet, melancholy, and weighty ballad than the light and whimsical “Free as a Bird” and “Real Love.” And while it is intensely moving to hear Lennon and McCartney’s then-and-now voices blend on the yearning chorus, Martin points out: “Yes, it almost sounds like John writing about Paul, but in a classic kind of John way. It is not, ‘I miss you.’ It’s, ‘Now and then, I miss you.’ That’s a classic John Lennon thing, it really is! Like, if you love someone and you say to them, ‘I miss you,’ that's different from going, ‘You know what? Now and then, I miss you.’ Classic John! And I think that’s what gives the song impact.”

In 2022, McCartney, Starr, and Martin secretly resumed completing “Now and Then,” bringing together Lennon’s crystal-clear isolated vocal; electric and acoustic guitar parts recorded by Harrison during the 1995 Anthology reunion; original backing vocals from the Beatles classics “Eleanor Rigby,” “Here, There and Everywhere,” and “Because”; and brand-new backing vocals and instrumentation by Starr and McCartney. The sessions were in fact so “hush-hush” that when the string arrangement, co-written by Martin, McCartney and Ben Foster, was recorded at Los Angeles’s Capitol Studios, the string players didn’t even know it was for a “last Beatles song,” thinking they’d been hired for a McCartney solo record.

Martin had already overseen the special edition boxed-set reissues of the Beatles’ Sgt. Pepper's Lonely Hearts Club Band, The White Album, Abbey Road, Let It Be and Revolver (the latter, released in October 2022, utilizing Jackson’s same “de-mixing” technology), so he was “used to doing these projects where I’m not allowed to talk about it, and the best way of dealing with that is just to act a bit stupid — which I can do really, really well!” But he still was “surprised at how it was all kept a secret”… until June 2023, that is, when McCartney himself teased the impending release of a “final Beatles record” to BBC’s Radio 4. “I told Paul, ‘Man, if anyone was going to leak this song existing, I’m happy it was you and not me!’”

In that instantly viral BBC interview, McCartney mentioned that “artificial intelligence” had been used to finish the lost track, which had fans crying blasphemy as they imagined some sort of creepy Lennon robot. “Jesus, man, it’s like people think we made a singing John Lennon,” Martin laughs. “All this machine did for us is clean the vocal from the piano and the TV that was on in the background. There’s no constructive AI going on in this track. … And despite the quality of AI and all that kind of shit that was said, we’re not trying to hide behind anything with this track. There’s probably less technology on this track than there is on most other songs that are out today! It is organic, it’s real, and it's definitely the Beatles. And that’s key. That’s what it is. Yes, this has been made possible because of the technology that’s been developed with Peter Jackson’s sound team, but it’s not a gimmick. What makes the song sound good is the artistry in it.”

John Lennon in 1979. (Michael Brennan/Getty Images) (Michael Brennan via Getty Images)

Martin reflects on the deep respect that McCartney showed for his late bandmates’ artistry while working on “Now and Then,” McCartney’s first official Beatles production credit. “Paul was like, ‘This is not a tribute record. We’re not trying to recreate other Beatles songs here,’” Martin recalls. For instance, when McCartney came up with a new Harrison-inspired slide-guitar solo, Martin says “he would spend a large amount of time trying to understand what George was trying to do on the guitar, going, ‘This is what George did, and we need to respect this, because he’s not here.’” (It should be noted that Harrison was the Beatle who most strongly advocated for abandoning “Now and Then” back in 1995. “George was always wary of pushing things too far — and also, George often wanted to get back to his garden,” says Martin. “George, I think out of all of them, really left the Beatles.”)

“We need to make sure that this is a band. They’re not here now, so we've got to damn right respect this band. We’re not making a song with no one. They’re on this recording, so we need to make sure damn sure that we hear them on this recording. Whatever they did before, we have to respect it completely,” Martin explains of the approach he and McCartney took in the studio. “And that was really important when we worked on John’s voice. What was great is that we improved the quality of John’s voice as we worked on the track, which gave us more space to do things. On the original demo Paul played me [that McCartney had already been working on], it started louder, because John’s voice was too fragile, in a way, on its own. And so suddenly, we had more and more John. And when you listen to the song now, it’s unmistakably John Lennon. It’s a John Lennon song. It gives you that resonance of, ‘This is him. This is his artistry here.’”

At the emotional climax of Murray’s mini-documentary, Now and Then – The Last Beatles Song, McCartney marvels, “All of those memories come flooding back. How lucky was I to have those men in my life and to work with those men so intimately, and to come up with such a body of music, to still be working on Beatles music in 2023? Wow.” Martin muses, “I speak with Paul, and it’s almost with regrets that he knows that the Beatles is the best it’s ever been. It’s the best band he’s been in. He never got that band back. It was his best band — and he’s been in some pretty good ones! But that magic they had was completely unique. In retrospect, they look back and go, ‘That was the best time, the best collaboration I’ve had.’ … And the fact of the matter is, Paul has said to me, ‘There are four Beatles, and only the four of us knew what it was like to be in the Beatles. No one else did, and no one else ever will.’

The Beatles in 1968. (Universal Music)

It seems McCartney had been chasing “Now and Then” since 1995, but Martin doesn’t believe its release, three decades after it was shelved and four whole decades after Lennon recorded the demo, brings any closure for either McCartney or Starr — because that was never the point. “I think they have closure anyway. I don’t think they're paralyzed; they certainly don't act like they are paralyzed by any sense of loss from what they've done. I think that's a different thing from just missing someone you love,” Martin explains. “And I just hope that ‘Now and Then’ makes [listeners] love and miss whoever they love and miss. I think as a song it's deeply bittersweet, and I just hope people enjoy it. It's as simple as that.

“That’s why we do this: We do all this for people who love and enjoy music. That’s the only reason why we do it. It's not as though the Beatles need recognition. It’s not as though Paul sits there thinking, ‘Oh, what’s the next marketing exercise for the Beatles?’ I just love the fact that he did this because he wanted to work with his mate again.”

A Peter Jackson-directed music video for “Now and Then,” featuring unseen performance footage provided by former Beatles drummer Pete Best and home movie footage provided by John Lennon’s son Sean and George Harrison’s widow Olivia, will premiere Nov. 3. The track will appear on an expanded, remixed edition of The Beatles 1967-1970 (“The Blue Album”), which will be reissued along with The Beatles 1962-1966 (“The Red Album’”) on Nov. 10.