Tenacious D will be filling in for the Beastie Boys at the Outside Lands Music & Arts Festival. The rock band / comedy duo will be headlining the last day of the festival(Aug. 30), with a performance that according to Jack Black "may shake the foundations of the...San Andreas (Fault) and California may be shaken loose from the rest of the country. The question is, when that crack in the earth happens and it comes between your legs, where ya goin'? Are you goin' with America or are you going with Cali island. You have to make a split decision or you're going down in the lava."

Tenacious and the Beasties have been friends since both played at shows to support Barack Obama's candidacy for president.

Black also noted that he and Kyle Gass have "been working hard on our hip-hop. Our next album is entirely rap and hip-hop with a sprinkle of maraca. We just laid down a hot...we're calling it the bomb track. It's a very powerful recording called 'Deph Starr'...so it has nothing to do with the 'Star Wars' (Death Star). It's kind of sci-fi, doomsday rock." There's no word yet on when a new Tenacious D project will be released."

The Outside Lands Festival will take place in San Fransisco's Golden Gate Park Aug 28 - 30. Along with Tenacious D, there will also be performances by Pearl Jam, the Dave Matthews Band, Black Eyed Peas, M.I.A., Modest Mouse, Incubus and Jazon Mraz.