Some months ago, I was sitting at the Port Authority Bus Terminal in New York with enough time on my hands that I actually noticed the music coming over the speakers in the ceiling. It was the scherzo from Schubert’s first piano trio. Schubert’s piano trios are among my favorite pieces in the universe, but as I listened, I found that I wasn’t relaxing; quite the contrary. The music sounded awful: tinny, hard-edged, aggressive. I wanted to get away.

I’ve long heard that the Port Authority is one of many public spaces across the country that uses classical music to help control vagrancy: to drive the homeless away. Listening to that Schubert rendition, I started to believe it.

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.

In a related story, a school in Derby, England, got into the news last year by using classical music to punish misbehaving pupils, forcing the disobedient to sit and listen to an hour of classical music. Behavior improved by 50 percent.

Like many things in classical music, these endeavors have entered the realm of conventional wisdom without being adequately studied. Installing speakers in a public space to play classical music usually involves some degree of physical improvement to the area and an increased police presence. How, then, can you determine that classical music alone is responsible for improving conditions? (At the Derby school, the students were subjected to the hour of classical music on a Friday evening, followed by a DVD about math and then the requirement of writing a paper about the experience. Classical music was perhaps not the least off-putting thing about the experience.) And can you really play classical music nonstop on city streets? In a 2011 article in the Huffington Post, the assistant police chief of West Palm Beach, Dennis Crispo, said of the program, which had been abandoned years before, “It really doesn’t have a lasting effect.”

(Ted Crow/For The Washington Post)

But the idea of classical music as a force for good fits right in with the widespread image — among classical music lovers, at least — of this art form’s exalted purpose. Classical music is often presented as a panacea. It can calm patients during surgery. It can socialize inner-city children and turn them into brilliant musicians (witness the El Sistema training program in Venezuela, which spawned conductor Gustavo Dudamel and a half-dozen other rising young stars). It can make you smarter (the so-called Mozart effect, which led to an unfortunate wave of bowdlerized music-for-babies CDs and videos starting in the 1990s). And now, it can fight crime, fulfilling its traditional elitist role by separating all of us good people who love classical music from the great unwashed, who flee like cartoon villains from the very sound of it.

There’s a kernel of truth to all of these suppositions, but some have been taken far out of context (the Mozart effect is a perfect example). And all of them go back to a fundamental idea about music that dates back to antiquity: the idea that this non­verbal art form has subliminal powers that can influence us in ways we aren’t quite aware of or can’t quite control.

Yet, using classical music to fight crime is not tapping into classical music’s inherent powers as much as its social attributes. Playing music in any space redefines that space, much as painting a mural on the side of a building affects the space around it: It is transformed from a no-man’s-land to a place with an identity, a kind of self-awareness. And music, perhaps more than any other art form today, is a tool of self-identification. For many people, especially young people, the kind of music you like is intimately related to how you dress, whom you hang out with, who you are. If the music that’s playing in a given space is not your music, then the space is not yours either. This is one reason that certain populations tend to avoid the concert hall, the same populations that 7-Eleven is trying to drive away.

Indeed, playing classical music to clear out public spaces is an act of supreme elitism: an attempt to “civilize” a space by making it unpleasant to people whose tastes differ from your own.

There’s nothing new about this use of music, neither is it limited to classical music. What we’re actually talking about is Muzak. Muzak sets out to improve the image of public spaces and, even more to the point, tap into music’s subliminal powers by inducing specific moods in its listeners, moods that will supposedly put them in the properly receptive frame of mind to consume whatever it is the space in question is selling.

“Founders of piped music and the science of how music affects the behavior of customers,” runs the tag line on the Muzak Web site. And its various playlists — “Uptown,” “Moodscape,” “Intermezzo” (guess which one is the classical one) — come with descriptions of the moods evoked (“simultaneously casual and elegant”) and suggestions as to which space might be appropriate for each list. (“Intermezzo,” the classical list, is recommended for banks, fine-dining establishments, museums, medical facilities and grocery stores, among others.)

By putting classical music in public spaces, stores and local authorities are effectively marketing those spaces and trying to induce people to behave more like model citizens. But in this context, the line between “classical music” and “Muzak” often becomes sketchy. If one thinks that Muzak is the default source for many of the places using classical music in this way, people’s aversion to it can be seen in a different light. Indeed, some sources report that Barry Manilow is as effective as Mozart in driving away unwanted groups of teens.

Recorded music in a public space has become a commodity, not an art. That people experience it as repellent may say little about their actual interaction with the music. When you’re passing through a space such as a bus terminal, music, however pleasing or noxious, tends to blend into the background. When you’re sitting still in the same space, the sound demands your attention — particularly when it’s a sound as dramatic as the Schubert trio. (Baroque music evidently has the best calming effect.)

The Schubert trio I was hearing was indeed part of a Muzak playlist, and it was, evidently, an undoctored recording. According to a Port Authority spokesman, Steve Coleman, the station plays classical music to please travelers, not to control vagrancy. But in that windowless, ugly space, with pigeons strutting across the grimy floor, announcements blaring unintelligibly over the loudspeaker and the sound system giving the music a harsh edge, as if impaling it on a jagged chunk of metal, my sympathies were all with the homeless people that such music is widely thought of as attempting to repel. If I’d had a choice, it would have driven me away, too.