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.
- Inception is one of the most famous examples, featuring a distinctive sound in the trailers that became memetic. Buttons for it exist.
- The Deep Note is the Ur-ominous sound before nearly every movie. You may know it better as the THX sound effect. Its ominousness comes from the fact that it sounds louder than it actually is, since it's made of a spectrum of frequencies that grow from small to large.
- The second The Avengers trailer had some instances of this, coupled with Loki's Hannibal Lecture. So did its third trailer.
- Transformers, particularly the trailers for Revenge of the Fallen and Dark of the Moon.
- TRON Legacy plays one as Sam first enters the Grid and sees a Recognizer. Its trailer isn't free of them either.
- Battleship's trailer used these upon reveal of the aliens.
- Prometheus used these, coupled with a strange howl taken from the original Alien's trailer.
- Rise of the Planet of the Apes: Sound familiar? The chord actually does show up in the film once, as the spear-wielding apes appear in a roof.
- Red Riding Hood goes for the horn.
- So does Battle: Los Angeles.
- A trailer for Saw: The Final Chapter
- District 9's second trailer featured pulses of many sizes.
- Many also in Immortals.
- It's not just the shark that attacks in Shark Night 3D.
- This trailer for The Thing (2011) has two different ones, a low one for suspense and a loud one for attack.
- Cowboys and Aliens's is fairly muted, but it culminates at 2:07.
- Diablo Swing Orchestra's "Justice for Saint Mary" (the final track off Pandora's Pinata). At 5:45 into the song, just after the final chorus, there are two low-pitched trombone notes, signaling to the listener that the song is about to kick it up a notch.
- In Halo 4, the orange pulses used to scan the UNSC Forward Unto Dawn create a noticeable rumble, possibly from the ship shaking from the scans.
- Endgame areas of Borderlands 2 use this liberally, especially in areas with volcanic activity or severe industrialization, as well as transitions into and out of combat.
- This trailer for [PROTOTYPE].
- Call of Duty: Modern Warfare 4: Another chord from Hans Zimmer himself.
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