Reverse Playback
This technique completely upends the natural evolution of a sound. For familiar or easily recognisable sounds, reversing playback turns the natural decay into a build-up toward a climax, placing the listener in a state of alert tension as they await a resolution.
Original sound: Fireworks
Exploring a fireworks recording with variations in playback direction and speed
When reversal is applied to less familiar, continuous sounds, it reveals new characteristics by highlighting aspects that remain hidden in normal playback.
Reversed sounds disturb our perception; a piano note, for example, played backwards seems much longer—because of its crescendo—than the same note played forwards.
Sonogram of playback-direction variations and pitch shifts of the “Fireworks” file
Reversal can also be combined with speed variation to create evolving sonic textures. This is the principle behind scratching in rap music—a manually controlled variation of speed and direction.