The method of production varies from one type of instrument to another. On brass instruments, it is usually created by means of a
mute, particularly with the harmon (also called a "wa-wa" mute) or plunger mute. Woodwind instruments may use "
false fingerings" to produce the effect. Any electrified instrument may use an auxiliary
signal-processing device, or pedal. Often it is controlled by movement of the player's foot on a rocking pedal connected to a
potentiometer. An alternative to players directly controlling the amount of effect is an '
auto-wah'. These devices, usually make harder hit notes more trembly with a more prominent wah wah effect. Wah-wah effects are often used for soloing or for creating a "wacka-wacka"
funk rhythm on guitar. Although these electronic means are most often on electric guitar, they are also often used on
electric piano. ==Theory==