Paul McCartney will fill the role of Kurt Cobain when he plays with the surviving members of Nirvana at the 12.12.12 concert for victims of Superstorm Sandy on Wednesday night.
The former Beatle will join Foo Fighters singer Dave Grohl and bassist Krist Novoselic on stage in New York to play a new song after secretly working with the pair.
A spokesman confirmed that Grohl recently asked McCartney to come along to "jam with some mates".
The former Beatle suggested they "just make something up" and found himself playing with Grohl on drums, bassist Novoselic and guitarist Pat Smear, who toured with Nirvana for the last six months of the band's career.
Kurt Cobain took his own life in April 1994.
McCartney said: "I didn't really know who they were. They are saying how good it is to be back together. I said: 'Whoa? You guys haven't played together for all that time?'
"And somebody whispered to me: 'That's Nirvana. You're Kurt.' I couldn't believe it."
The Rolling Stones, Jon Bon Jovi, Eric Clapton, Billy Joel, Bruce Springsteen and Kanye West will also play at the 12.12.12 concert for victims of Superstorm Sandy at Madison Square Garden in New York.
• This article was amended on 12 December 2012 - the original claimed that Grohl and Novoselic hadn't played together for 20 years
