The last "new" Beatles song, "Now and Then," was released on Thursday, 60 years after the onset of Beatlemania. 

The fresh release features the voices of all four original Beatles performers, with surviving members Paul McCartney and Ringo Starr essentially finishing what was initially an old demo recording by John Lennon. The track draws in many ways on group's signature style and features emotional chorus where, together, McCartney and Lennon's voices sing, "I miss you."

Listen: The Beatles - Now And Then (Official Audio)

The original "Now and Then," recorded by Lennon more than 40 years ago, came from the same group of demo recordings that his former bandmates used to create the songs "Free As a Bird" and "Real Love" in the mid-90s.

Written by Lennon in 1978 and and completed by McCartney and Starr last year, "Now and Then" also features sounds by the band's late guitarist George Harrison, using pieces of one of his studio recordings from 1995. McCartney also added a new string guitar part with help from Giles Martin, the son of the late Beatles producer George Martin, the Associated Press reported last month. 

How did The Beatles make a new song?

"Now and Then," in part, used artificial intelligence to separate out Lennon's original vocals before incorporating McCartney and Starr's musical additions in the studio last year. A short documentary film chronicling the making of "Now and Then" was released Wednesday on The Beatles' official YouTube channel, ahead of an upcoming music video which is expected to drop roughly 24 hours after the release of the song itself.

"'Now and Then's eventful journey to fruition took place over five decades and is the product of conversations and collaborations between the four Beatles that go on to this day," reads the short film's YouTube description. "The long mythologised John Lennon demo was first worked on in February 1995 by Paul, George and Ringo as part of The Beatles Anthology project but it remained unfinished, partly because of the impossible technological challenges involved in working with the vocal John had recorded on tape in the 1970s."

"For years it looked like the song could never be completed," it continues. "But in 2022 there was a stroke of serendipity."

In the documentary, both McCartney and Starr marveled at how clearly Lennon's voice comes through in the newly-packaged version of "Now and Then."

"All those memories came flooding back," said McCartney. "My God, how lucky was I to have those men in my life? To still be working on Beatles music in 2023? Wow."

Starr added, "It was the closest we'll ever come to having him [Lennon] back in the room ... Far out."

Which Beatles are still alive?

Two of the four original members of The Beatles are still alive: McCartney, who played bass guitar for the group and shared both songwriting responsibilities and lead vocals with Lennon, and Starr, the band's drummer. At 81 and 83 years old, respectively, McCartney and Starr have continued to make music as solo artists, and in collaborations with other performers, through the years. 

Lennon, who served as the co-lead songwriter and vocalist, and rhythm guitarist, for The Beatles, died in 1980 at 40 years old. He was shot several times and fatally wounded by Mark David Chapman as he walked into his New York City apartment building on Dec. 8 of that year. Lennon's death is remembered as one of the most infamous celebrity killings of all time.

Harrison, The Beatles' original lead guitarist, died on Nov. 29, 2001, after battling cancer. He was 58 years old. 

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