History was made at the end of tonight's 12-12-12 Concert for Sandy Relief when Sir Paul McCartney took the stage with Nirvana's two surviving members -- drummer Dave Grohl and bassist Krist Novaselic -- as well as guitarist Pat Smear. It was the Nirvana reunion everyone had been talking about ... sort of. They didn't do a Nirvana song; instead, the foursome performed a brand new one.

The tune that Grohl, Novoselic and Smear played with the Beatles legend is reportedly called 'Cut Me Some Slack.' It wasn't some Nirvana classic or deep album cut, as much of the pre-show social media chatter suggested.

“So recently, some guys asked me to go and jam with them,” McCartney said midway through his show-closing set, and everyone knew what was coming. "So I showed up, ready to jam. In the middle of it, these guys kept saying, 'We haven't played together for years.' So, you know, I finally understood that I was in the middle of a Nirvana reunion!"

Grohl was grinning like a schoolboy when he appeared, and the group bashed out a raw, sludgy, frenetic rocker that reminded us of Nirvana. Whether it was actually a "reunion" is open to debate, but either way, this was rock history in the making. Seeing Grohl smash away on the skins and sing backup to McCartney was one of those pinch-us-is-this-really-happening moments.

Watch Paul McCartney Perform With Dave Grohl and Krist Novaselic at the 12-12-12 Concert

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