Now that Foo Fighters' James Moll-directed doc Back and Forth has won the Grammy for best longform video, frontman Dave Grohl is getting behind the camera for his own passion project. He will chronicle the history of Van Nuys studio Sound City, where Nirvana's Nevermind and other game-changing albums were recorded. Among the alums he's interviewing: Trent Reznor, Tom Petty and Stevie Nicks. … Beware of personal trainers recommended by Swedish hitmakers. Island Def Jam and Universal Republic chairman Barry Weiss learned that the hard way on Grammy weekend. After a session with music producer Max Martin's muscle man, the exec was so sore, he had a hard time navigating the crowd at Roc Nation's Soho House brunch. Martin, meanwhile, is in town to work on new music with Justin Bieber. … Banksy protege Mr. Brainwash turned into a fanboy when he spotted Slash at Clive Davis' pre-Grammy party. "I want, eh, peace with you," he told the rocker in his thick French accent. "What?" replied Slash, confused. "Piece, I want to make a piece with you." No numbers were exchanged. … The American Idol bond is strong. Look no further than the post-Grammys hang at Jerry's Deli in Beverly Hills, where Steven Tyler and Carrie Underwood dined with a posse of seven. The two share manager Simon Fuller. … Speaking of talent shows, everyone has an opinion on who should step into The X Factor's vacated seats. Jennifer Hudson's vote? "Barbra Streisand. Who wouldn't want to learn from her?" she said at the Gucci Timepieces and Jewelry music preservation event at the Grammy Museum on Feb. 11. Meanwhile, Sharon Osbourne is preparing for Howard Stern's arrival on America's Got Talent. "I'm excited because he and I have exactly the same taste in music," she told THR. Will Piers Morgan be missed? Says Osbourne, "We'll always have Piers in our lives because we have to watch him every night now, don't we?"