To many people, classical music is the perfect background music: soothing, attractive, undemanding. But for some time, it’s also been used as a form of crowd control: a kind of bug spray for people you don’t want hanging around. Early attempts in this direction date to the mid-1980s, when a 7-Eleven began playing music in the parking lot as a deterrent to the crowds of teenagers congregating there. Plenty of stores continue to use the technique, and other examples have been cropping up sporadically ever since. In 2001, police in West Palm Beach, Fla., blasted Mozart and Beethoven on a crime-ridden street corner and saw incidents dwindle dramatically. In 2010, the transit authority in Portland, Ore., began playing classical music at light-rail stops, and calls to police dropped. When the London Underground started piping classical music into its stations in 2005, physical and verbal abuse by young people (however you define THAT) declined by 33 percent.