Yesterday, rumors circulated that Paul McCartney would be performing with the surviving members of Nirvana (Dave Grohl, Krist Novoselic, and touring guitarist Pat Smear) at the 12.12.12 Concert in Madison Square Garden. A few hours later, Novoselic not only confirmed the performance, but also revealed that they would be performing a new song. And sure enough, last night’s hurricane relief show featured Sir Paul himself onstage with the closest thing to a Nirvana reunion we’ll likely ever see.

As it turns out, the new song they performed called “Cut Me Some Slack” was one of the many collaborations recorded for the soundtrack to Grohl’s Sound City documentary. And Novoselic’s description of the new tune via tweet is pretty dead on. In other words, “Cut Me Some Slack” is pretty damn good.

Watch McCartney and members of Nirvana performing “Cut Me Some Slack” in the video above (at least until it gets taken down from online). A trailer for the song (posted on Cutmesomeslack.net) can be seen after the jump.