The long-awaited "final" Beatles song - featuring each member of the Fab Four - is due to be released next week thanks to new technology.
"Now and Then" was written and sung by John Lennon in the late 1970s, but was never released.
A software developed for Peter Jackson's documentary Get Back has now been used to separate out Lennon's voice from the cassette recording, which has the parts recorded by the three other Beatles added to it.
Sir Paul McCartney has described the release as "emotional" and "exciting".
Beatles expert and journalist Martin Lewis spoke to Corin Dann.
