John Williams created the ultimate movie legend of fear with just two notes for 'Jaws.' While the theme is played by the full orchestra, the core 'heartbeat' is driven by the low strings, specifically the cellos and double basses. Williams wanted a sound that was 'grinding' and 'unstoppable,' like the shark itself. He chose the lowest register of the cello to create a primal, visceral vibration that triggers a fight-or-flight response in the audience. When director Steven Spielberg first heard the two-note theme on a piano, he thought it was a joke. However, once he heard it played by the deep, dark voices of the cellos, he realized it was the sound of a cinematic legend. This proved that simple, low-frequency sounds are often the most terrifying.