Judging from the veracity of Dave Grohl's whipping hair, Wednesday night's Nirvana jam session with Paul McCartney a the 12.12.12 Concert for Sandy Relief went over swimmingly. The promised marriage of the most important band ever (The Beatles) and the most influential of the '90s (Nirvana) resulted in a thrilling few minutes of spontaneous, raw magic.

After a quick story about "jamming" with a few guys recently, McCartney said it dawned on him that he was "in the middle of a Nirvana reunion." After introducing Grohl, Krist Novoselic and Pat Smear to the stage, the quartet tore into a thick and bluesy track called "Cut Me Some Slack," about having fun or rolling into town (or something).

Grohl appeared at home behind the drum kit and Novoselic, wearing a loudly shiny shirt on his tall and bearded frame, bopped around in his trademark slunched-over stance.

"Cut Me Some Slack" will be included on the soundtrack of Grohl's new movie, "Sound City Movie." Hear a snippet: