Just as the Beatles used their timeless songs in the 1960s to take millions of listeners across the universe on a magical musical mystery tour, Oscar-winning Lord of the Rings trilogy director Peter Jackson has taken millions of viewers worldwide on a magical cinematic mystery tour in this century.

So what happens when these two worlds and creative forces intersect, 51 years after the Beatles acrimoniously split up in 1970?

“It’ll blow your mind!” said Jackson, a lifelong fan of the most famous and influential band in rock-and-roll history.

And what happens when that unlikely intersection — which has resulted in Jackson’s engrossing new film documentary, “The Beatles: Get Back” — comprehensively chronicles the month of January 1969?

That was when the fabled band simultaneously made its penultimate album, “Let It Be,” and an identically titled film documentary.

The four Beatles — John Lennon, Paul McCartney, George Harrison and Ringo Starr — undertook both projects despite the rapidly rising tensions that soon led them to permanently disband. They had no way of knowing the film crew they had hired to capture the creation of their new album and final concert would end up documenting what many regard as the Beatles’ painful on-screen divorce.

Why would fans want to revisit such a downward spiral on film again? Why would Jackson devote four years of his life to it?

These questions are answered this weekend, as “Get Back” streams on Disney Plus. It’s being released in three installments, the first of which premiered Thursday and continues Friday and Saturday; together, the project totals more than six hours.

The original “Let It Be” film clocked in at a fleeting 80 minutes and included just 21 minutes of the Beatles’ final public performance, an impromptu winter gig on a London rooftop. “Get Back” boasts the entire 42-minute performance by the band and guest keyboardist Billy Preston, who all but joined the Beatles as “Let It Be” was being filmed.

Jackson’s documentary follows the October release of a 240-page “The Beatles: Get Back” book and a new “Let It Be Special Edition” box set. The latter includes five CDs with 57 songs, one Blu-ray disc and a 100-page book. It is also available in a vinyl edition and in smaller CD iterations.

“Get Back” was originally set to open in theaters last year as a 2½ -hour feature film but was pushed back by the pandemic. With more time unexpectedly on his hands, Jackson transformed his feature film into the six-hour epic.

He culled “Get Back” from nearly 60 hours of previously unseen footage that was shot in 1969 for director Michael Lindsay-Hogg’s briefly released and widely criticized “Let It Be” documentary. With few exceptions, while making “Get Back,” Jackson deliberately avoided using any of the footage that was featured in Lindsay-Hogg’s film — the better to provide viewers a captivating new experience with one of the most-documented rock bands of all time.

“I tried to make a very honest movie,” he said.

He would like to release an expanded director’s cut sometime in the future, but there are no current plans to do so. At one point, Jackson’s favorite version of his “Get Back” film clocked in at 18 hours.

Painstaking work

The differences between “Get Back” and “Let It Be” are profound, even though they use the same source material. “Get Back” also draws from nearly 120 hours of previously unheard audio recordings.

“The footage was shot in January 1969, and the Beatles didn’t really break up until September of that year,” Jackson, 60, noted during a recent Zoom interview from his home in the New Zealand capital of Wellington.

“So it’s not that the band breaks up then (in January), even though there are ups and downs in that month. I didn’t have to manipulate the story. Because, fortunately, the story was built into the (existing footage) — the story of how they set out to do a recording and a live show, and have 14 new songs written in two weeks. . . . I was lucky the film already had enough drama from the real events that took place.”

Jackson and his team started work in 2017 on “Get Back.” They carefully restored, upgraded and enlarged the grainy original 16-millimeter 1969 “Let It Be” film footage so that it now pops with vibrant color.

They also developed a new form of AI audio engineering — a sort of sonic forensics — they dubbed “MAL” (a play on the AI super computer HAL in the 1968 film “2001: A Space Odyssey”). The name honors the Beatles’ beloved road manager and principal assistant, Mal Evans, who shares some screen time with the band in “Get Back.”

Using MAL, Jackson and his colleagues were able to painstakingly and precisely isolate each and every audio track — be it musical instrumentation, singing or studio chatter — from the original mono recordings made for most of “Let It Be.”

“What we’ve managed to do is split it all apart in a way that is utterly clean and sounds much better,” Jackson said.

Released in 1970, “Let It Be” seemed to be shrouded in literal and figurative darkness — apart from the truncated scenes of the rousing London rooftop concert.

“Get Back” balances “Let It Be’s” gloomy, downhill-and-shadows tone with scenes of lightness and levity. It also takes a deep dive into the complex human emotions and egos that ultimately drove the Beatles apart for good, after they recorded their final album, “Abbey Road,” later in 1969. (Because “Abbey Road” was released before “Let It Be,” many fans at the time understandably thought “Let It Be” was the last album the band made.)

For some viewers, then, “Let It Be” almost qualifies as a real-time wake for the Beatles, starring the Beatles.

In a 1970 interview, Lennon said of filming “Let It Be”: “It was hell . . . the most miserable session on earth.” McCartney, speaking in 1995, said: “We had terrible arguments (resulting in) the breakup of the Beatles on film instead of what we really wanted. It was probably a better story — a sad story, but there you go.”

And in a 1995 San Diego Union-Tribune interview, longtime Beatles album producer George Martin said: “ ‘Let It Be’ was very unhappy for everybody. George (Harrison) wanted to leave (the band), and there was even a bit of fisticuffs. And John was very difficult; he didn’t take much notice of anybody and he was being very pushy. I did not enjoy it one bit.”

Context is everything

Poignancy is one of the most vital components in Jackson’s “Get Back.” Even more crucially, he also provides much-needed context — a quality largely missing from “Let It Be” — thanks to the trove of previously unseen footage and careful editing.

“Get Back” doesn’t shy away from the tense and uncomfortable scenes that presaged the Beatles’ implosion. But it also opens a welcome new lens that is far richer, more nuanced and intimate than “Let It Be.” And “Get Back” offers both lighthearted and moving moments to illustrate the deep bonds that united the four Beatles, even as their band neared its demise.

What results is not a remake or recasting of history, but a broadening of it. “Get Back” doesn’t paint a brand-new picture, but it greatly expands upon the often bleak one “Let It Be” painted.

It has already proved eye-opening for McCartney, 79, and Starr, 81. (Lennon was killed by a gunman in 1980; Harrison died of cancer in 2001.)

“I had always thought the original film ‘Let It Be’ was pretty sad as it dealt with the break-up of our band, but the new film shows the camaraderie and love the four of us had,” McCartney writes in his foreword for the “Let It Be Special Edition” box set’s book.

“It also shows the wonderful times we had together, and combined with the newly remastered ‘Let It Be’ album, stands as a powerful reminder of this time. It’s how I want to remember the Beatles.”

Speaking now of McCartney and Starr’s reaction to “Get Back,” Jackson said: “It’s not the story the way they remember parts of it, because they don’t remember it; it was more than 50 years ago. They lived through it, but they can’t remember it — except the miserable part of breaking up in 1970 and all the acrimony.

“But they thought it was a very accurate portrayal of the band and that made me think: ‘I’ve achieved my goal.’ We could balance things and add context, which is critically important in this film.”

Because the first “Get Back” preview released last year was so upbeat, some observers worried Jackson was sanitizing an undeniably messy and bitter period in the Beatles’ storied history. It’s a notion he is quick to dispute.

“There are a lot of things in ‘Get Back’ that are actually tougher and more raw and honest than in ‘Let It Be,’ ” he said.

“For example, Michael Lindsay-Hogg wasn’t allowed in 1969 to show George (Harrison) leaving the band and walking out for a few days. He filmed that and has scenes of George announcing he’s quitting (the band). Michael wasn’t allowed to show that, but we do. We had no restrictions.”

Lindsay-Hogg, conversely, was given very specific directives before “Let It Be’s” release, regarding what he could and could not include.

“The Beatles were icons, these four mythic guys,” Jackson said. “Their music still makes me smile and still means the same to me as it always had. But after making this film, they’ve come down off the pedestal and are no longer these mythic figures to me. They’ve become these four human beings now.”

— San Diego Union-Tribune/Tribune News Service

George Varga is the pop music critic at the San Diego Union-Tribune. “The Beatles: Get Back” continues streaming on Friday and Saturday on Disney Plus.