The IWW (Industrial Workers of the World) certainly believed that songs could change things, and I agree with them! Art T. has already alluded to this in putting Joe Hill on his list. . . the subtitle to their songbook is "to fan the flames of discontent" and sometimes a good protest song can act as a seed crystal (read Vonnegut's novel Cats Cradle to see what a seed crystal can do!) to crystallize people's ideas.