Unseen footage of members of the Beatles singing material by pop rivals the Rolling Stones is to be released.
Harrison and Starr were filmed playing a Stones song backstage
Beatles George Harrison and Ringo Starr were filmed playing Jumping Jack Flash before Harrison's New York Concert for Bangladesh, to be released on DVD.
Guitarist Eric Clapton joined in as they prepared for the 1971 benefit gig.
"We were lucky enough to discover this fantastic rehearsal footage which had just been sitting in the archive for 34 years," said editor Claire Ferguson.
"It was an incredible treasure trove," she told The Independent newspaper.
Jumping Jack Flash was a number one hit for the Rolling Stones in 1968.
Although the Rolling Stones recorded Beatles songs, and members Mick Jagger and Keith Richards sang backing vocals on their hit All You Need Is Love, the Beatles did not record Rolling Stones material.
The late George Harrison's Concert for Bangladesh at Madison Square Garden raised money for Unicef and was widely regarded as the first large-scale fundraising concert.
Also featuring Bob Dylan and Ravi Shankar, the concert is due to be released on DVD in October.