The new song that the "reunited" Nirvana and Paul McCartney premiered during Wednesday's 12-12-12 Hurricane Sandy Benefit Concert in New York City was composed for inclusion on the soundtrack to Dave Grohl's forthcoming 'Sound City' documentary. The tune, titled 'Cut Me Some Slack,' was recorded several months ago as one of several collaborations Grohl took part in while working on the soundtrack, titled 'Sound City - Real to Reel.'

Grohl's other collaborators included Trent Reznor, Josh Homme, Fleetwood Mac's Stevie Nicks, members of Foo Fighters, Rage Against the Machine and more. 'Cut Me Some Slack' is currently available for purchase as a download on iTunes. Ex-Nirvana bassist Krist Novaselic described the song in a Twitter post as "kind of 'Helter Skelter' meets 'Scentless Apprentice.' It rocks with a heavy groove. St. Paul is powerful."

The 'Sound City' documentary itself will premiere at the Sundance Film Festival early next year and be available both via digital download/stream and in theaters starting Feb. 1.