The new track, called "Now And Then," became available on Thursday and comes in at just over 4 minutes long. It's part of a single paired with "Love Me Do," the very first Beatles single that came out in 1962 in England.
"Now and Then" was written and sung by the late John Lennon – part of a batch of unreleased demos that were later taken by his former bandmates to construct the songs "Free As a Bird" and "Real Love," released in the mid-1990s.
The new song was later developed and worked on by Paul McCartney, Ringo Starr, and the late George Harrison in the same sessions, but technological limitations stood in the way.
Over four decades later, "Now and Then" was finally finished by the surviving duo with the help of artificial intelligence.
Director Peter Jackson "separated" Lennon's original vocals from a piano used in the late 1970s. The much clearer vocals allowed McCartney and Starr to complete the track last year, according to the band.
The new single contains guitar that Harrison had recorded nearly three decades ago, a new drum part by Starr, with McCartney's bass, piano and a slide guitar solo he added as a tribute to Harrison, who died in 2001. McCartney and Starr sang backup.
McCartney also added a string arrangement written with the help of Giles Martin, son of the late Beatles' producer George Martin.
As if that wasn't enough, they weaved in backing vocals from the original Beatles recordings of "Here, There and Everywhere," "Eleanor Rigby" and "Because."
On Wednesday, a 12-minute film that tells the story of the new recording was also released.
‘There it was, John’s voice, crystal clear’
Harrison's widow, Olivia, said he felt in the 1990s that the technical problems made it impossible to release a song that met the band's standards. With the improvements, "he would have wholeheartedly" joined Paul and Ringo in completing the song now if he were still alive, she said.
McCartney called the development of the song "quite emotional."
"There it was, John's voice, crystal clear," McCartney said in the announcement of the new song. "It's quite emotional. And we all play on it, it's a genuine Beatles recording. In 2023 to still be working on Beatles music, and about to release a new song the public haven't heard, I think it's quite an exciting thing."
Later in November, expanded versions of the Beatles' compilations "1962-1966" and "1967-1970" will be released. "Now And Then," despite coming much later than 1970, will be added to the latter collection.
The surviving Beatles have skillfully released new projects, like remixes of their old albums that include studio outtakes and Jackson's "Get Back" film, usually timed to appeal to nostalgic fans around the holiday season.
This year, it's the grand finale of new music.
"This is the last track, ever, that you’ll get the four Beatles on the track. John, Paul, George, and Ringo," Starr said in a recent interview with The Associated Press.
This story was reported from Cincinnati. The Associated Press contributed.