Paul McCartney has revealed that artificial intelligence is being used to put together what he is calling "the final Beatles record".
He was interviewed on BBC Radio 4's current affairs Today programme and said that technology had been used to "extricate" John Lennon's voice from an old demo so the song could be completed.
He did not name the song, but it is expected to be a 1978 Lennon tune called Now And Then.
"We just finished it up and it'll be released this year," McCartney explained.
It had already been considered as a possible "reunion song" for the Beatles in 1995, as they were compiling their career-spanning Anthology series.
Paul had received the demo a year earlier from Lennon's widow, Yoko Ono. It was one of several songs on a cassette labelled 'For Paul' that Lennon had made shortly before his death in 1980.
The basic recordings were largely made using a boombox as Lennon sat at a piano in his New York apartment.
Cleaned up by producer Jeff Lynne, two of those songs - Free As A Bird and Real Love - were completed and released in 1995 and 1996, marking the Beatles' first "new" material in 25 years.
The band also attempted to record Now And Then - but Lynne recalled: "It was one day - one afternoon, really - messing with it.
"The song had a chorus but is almost totally lacking in verses. We did the backing track, a rough go that we really didn't finish."
In 2009, a new version of the demo, without the background noise, was released on a bootleg CD. Fans have speculated this recording may not have been available in 1995, suggesting it was stolen from Lennon's apartment, along with other personal effects, after his death.
In the intervening years, Paul has repeatedly talked about his desire to finish the song.
The turning point came with Peter Jackson's Get Back documentary, where dialogue editor Emile de la Rey trained computers to recognise the Beatles' voices and separate them from background noises, and even their own instruments, to create "clean" audio.
The same process allowed McCartney to "duet" with Lennon on his recent tour, and for new surround sound mixes of Beatles' Revolver album to be created last year.
"He [Jackson] was able to extricate John's voice from a ropey little bit of cassette," McCartney told BBC Radio 4's Martha Kearney.
"We had John's voice and a piano and he could separate them with AI. They tell the machine. 'That's the voice. This is a guitar. Lose the guitar.'
"So when we came to make what will be the last Beatles' record, it was a demo that John had [and] we were able to take John's voice and get it pure through this AI.
"Then we can mix the record, as you would normally do. So it gives you some sort of leeway."
