As a result of Web sites and technology companies setting up shop in the San Franciscos Bay Area, rent and real estate prices have skyrocketed. Numerous music venues have closed in the past few years, the noted Church of Saint John Coltrane was booted from its 30-year home, and the popular Downtown Rehearsal studio complex was sold to a developer in September, forcing the eviction of more than 150 bands — some 2,000 musicians.

Kirk Hammett urged the crowd to vote Tuesday for San Francisco's Proposition L, a ballot initiative intended to limit dot-com office space.

"Being someone who came out of the San Francisco music scene, I felt that I had to get involved and do what I can to prevent the Mission [District] from being turned into some bland business district," Hammett said backstage. "It's taking small steps right now to help out all of my fellow musicians, artists and nonprofit organizations to make sure that they don't just fall by the wayside by all these dot-commers and the new dot-com economy that's taking over the city."

Hammett said he has been helping organize a benefit concert to raise money for a new non-profit that would buy and run rehearsal space.

The crowd then packed in close as Green Day took the stage. The singer stopped in the middle of one descending, swing-style crunch to make a dedication to Hammett by blasting out the intro to Metallica's "Master of Puppets."

"I'm sorry — I don't work behind a computer, I work behind a fucking guitar," Green Days' Armstrong said, announcing that the band's set list had run out, then begging requests from the audience.