Is there an American classic rocker so uniformly beloved as Tom Petty? We'd argue that there isn't — songs like "American Girl" and "Free Fallin'" are touchstones of U.S. culture, and his Greatest Hits may be the best road-trip record of all time. To celebrate Petty and his ludicrously thick songbook, a vast assemblage of great local musicians gather at the Fillmore to put their own spin on the Petty catalog. The list of performers includes Boz Scaggs, Two Gallants, Tom Johnston of the Doobie Brothers, Jody Porter of Fountains of Wayne, and many, many more. Petty Fest's arrival in San Francisco this week is a NorCal extension of a New York tradition that began with small shows honoring Dylan and the Stones. No disrespect to those greats, but hearing Petty tunes at the Fillmore should be a whole other order of pleasure.