There's a world of difference between a horror movie and a comedy—the former scares you half to death while the latter leaves you rolling on the floor with laughter. But try watching them without the background music and you just might decide they're not so different after all. Music and movies have been closely connected since the beginning of the film industry—even before the voices of actors were recorded. In movies, music helps to provide a sense of time and place, convey ideas about the characters and, most importantly, draw emotions out of the audience.
Studies have long shown that our heart rates and anxiety levels rise and fall depending on the speed of the music we hear. Using this knowledge, composers use sudden changes in film music speed to create fear among audiences. Slowing the speed of the music will have the opposite effect, bringing about a sense of peace or a dreamlike quality. The use of dissonant (不和谐的) tones and noises is another technique that heightens tension. Humans naturally become unnerved when we hear dissonant sounds because such noises are usually associated with danger, like those that animals make to warn against predators (捕食者).
As crucial as it is, the best film music is subtle. All that audiences are supposed to feel is a heightened sense of emotion—they shouldn't realize what's causing it. Only when the music is taken out of the film should audiences understand its effects.
In keeping with this principle, some filmmakers are even using what's called "infrasound" (次声波) to arouse fear. While we may not be able to hear it because its frequency is below the range of the human ear, infrasound has been proven to cause anxiety, tremble and even sorrow. For example, infrasound was used in the soundtrack of the 2007 horror movie Paranormal Activity, and audiences reposed extremely high fear levels despite the 1ack of action throughout the movie. "It doesn't affect everyone equally," said British science writer Philip Ball, author of The Music Instinct, but he predicted that "we will see more of it used in movies in the future".
