I get this argument if we are all riding in the woods or something but do your really care about people having music in the city? There are a lot of mobile sound systems in SF and I love riding around hearing them all. There are even two different dudes who practice drums on FULL kits at two different spots in Golden Gate Park on the weekend. It always gives me a little extra boost when I go by them. Now if I hauled my bike up to Marin to take a scenic ride it might be a different story but who cares in the city?