Tremolo pedals modulate volume to create a pulsating effect, one of the earliest guitar effects. Initially built into vintage amps, standalone pedals offer greater control. Significant models include the Boss TR-2, Fulltone Supa-Trem, Strymon Flint, and JHS Tidewater. Used in surf rock, blues, country, and ambient music, tremolo can add subtle movement or intense choppiness. It's ideal for enhancing rhythm sections or adding a vintage feel, making it a favorite for both classic and experimental styles.