The song, titled "Now and Then," was played on BBC radio just after 2 pm local time and simultaneously released on streaming platforms.
With the help of digital technology, the track features both John Lennon, who was shot dead in 1980, and George Harrison, who died from lung cancer in 2001.
With new contributions from Paul McCartney, 81, and Ringo Starr, 83, the song will be the track released by possibly the most influential and bestselling musical group of the 20th century. The barrel’s bottom has been officially scrapped.
The song was a demo made by Lennon in his New York City flat. It could never be released because the technology was not available which could separate his voice from the other noises in the room.
McCartney delighted fans in June by announcing the final track was on the way, revealing that he was working with movie director Peter Jackson to isolate and enhance a low-quality cassette tape of John Lennon singing and playing piano in his New York apartment in the late 1970s.
The other three had a crack at making it viable but it sounded rubbish. However, they still had Harrison’s recording for those sessions.
Harrison said in the mid-90s (to the utter joy of Apple’s PR bunnies), “I hope that people take all my crap old demos when I‘m dead and turn them into hits.” So it looks like they did.
McCartney said that he had some doubts about using Lennon’s voice.
"Every time I thought like that I thought, wait a minute — let’s say I had the chance to ask John, ‘Hey John, would you like us to finish that last song of yours?’ I’m telling you, I know what the answer would have been ‘Yeah!’ He would have loved it,” he said.
Sean Ono Lennon, John and Yoko's son, told the BBC: "My dad would have loved that because he was never shy to experiment with recording technology. I think it's really beautiful."
The official review from the Fudzilla team was that the track was delightfully mediocre.
“Well I was expecting it to be more mediocre. I didn't expect my eyes watering though.,” a former sub-editor said.