10 Horror Movie Tropes That Prove "If It Ain't Broke, Don't Fix It"
9. The Scare Chord
The "scare chord" is a musical or sound based non-diegetic (nothing in the film is causing the noise) example of dissonance that is designed to amplify the shock value of an onscreen event, such as a shadow moving in the dark, or a 'dead' body's eyes snapping open.
The scare chord's purpose is to ensure that in the unlikely event that whatever has happened onscreen hasn't frightened the audience by itself, then this musical device will definitely be enough to do the trick.
Usually, the scare chord is preceded by a lull in any onscreen action, and so acts as a musical jump scare.
Trope Examples: Psycho (1960), Jaws (1975), Sweeney Todd: The Demon Barber of Fleet Street (2007), The Shining (1980)