A chord used in trailers to build up mystery and suspense.
Trailers love to play up excitement and mystery, and one favorite way to do this by tickling the ears with an unusual sound. One of these sounds is the Previews Pulse. It is often created by an instrument known as a blaster beam which creates a single chord which ends up sounding technological and mysterious. Other methods are through mixing several instruments, usually bass, or altering the sound of a horn. These "pulses" are used in trailers to create a feeling of sudden tension, similar to a Scare Chord, but are rarely used in the movie itself, as it may be distracting. A trailer that uses them is often made up of rapidly cut snippets, with the chord announcing with each new scene.