The Brown Note?
Music plays a pivotal role in how certain scenes are told. One of the most popular examples of this is during the opening credits scene in The Social Network, where the sad music sort of makes the audience feel dread and alone. But the director of Irreversible took music notes to another extreme.
Throughout the movie, viewers would claim that they felt sick and uneasy while watching parts that involved no violence at all. It turned out that the filmmaker Gaspar Noe would insert a note that hummed under 28 Hz. This would instill an inexplicable feeling that something was about to go down.