The Bicycle Music Festival returns to San Francisco this weekend for its fourth year. Started in 2007, the BMF touts four features unique to any music festival the city has to offer. First, the PA system is powered entirely by people pedaling stationary bikes. Second, organizers and volunteers transport all equipment to and from the festival sites on bicycle. Third, the event takes place at multiple locations throughout the city. This year the event starts at Speedway Meadow at noon, becomes mobile for the parade to the second spot at 5, and finishes out the evening at Showplace Triangle (16th & Wisconsin). Finally, the parade itself features musicians performing while they bike through the city thanks to Rock the Bike's Soul Cycle audio-equipped bikes. Performers include Fossil Fool of Rock the Bike, the city's mobile bike rapper; singer/songwriter Sean Hayes; and Flamenco group LoCura. The event, as always, is free—unless, of course, you count the manpower you volunteer to keep the music going!