Tonight’s concert for victims of superstorm Sandy is set to become a slice of music history with the news that Paul McCartney will sing with former members of Nirvana.

McCartney will be standing in for the late Kurt Cobain when he sings with Dave Grohl and Krist Novoselic, who have not performed together for more than 20 years.

'Somebody whispered to me: 'That's Nirvana. You're Kurt.' I couldn't believe it.'—Paul McCartney

They join a high-profile lineup for the benefit concert in New York, including the Rolling Stones, Billy Joel, Jon Bon Jovi, Eric Clapton, Bruce Springsteen and Kanye West.

Grohl recently invited McCartney to come along to "jam with some mates," according to reports in the British press.

The group, with Grohl on drums, Novoselic on bass and Pat Smear, who toured with Nirvana, on guitar, ended up creating a new song with the former Beatle.

"I didn't really know who they were,” McCartney said. “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."

Concert to be streamed online

The 12-12-12 concert at Madison Square Garden will be available on television or online to about two billion people, according to James Dolan, one of the producers. None of the main U.S. networks is carrying it, but 34 smaller networks are, including HBO and Showtime.

The sold-out benefit is being produced by movie mogul Harvey Weinstein, who said the show has raised $30 million so far for victims of the storm that hit the east coast of the U.S. on Oct. 29. Thousands of people had their homes destroyed when Sandy struck New York state and New Jersey.

McCartney’s appearance with the remaining members of Nirvana (Cobain died in 1994) will come at the end of the evening, along with a performance by all the artists together onstage. In addition to the former Beatle, British rock royalty such as the Who, Chris Martin and Roger Waters are set to perform.

Some of the segments about storm victims will be introduced by Sean Combs, Brian Williams, Jon Stewart, Jamie Foxx, Chris Rock, Chelsea Clinton, Adam Sandler, Seth Meyers and Leonardo DiCaprio.

The concert begins at 7.30 ET tonight.