Make your Mustang amp or multi-effects unit more fun, expressive and versatile. The EXP-1 Expression Pedal is a dynamic dual-mode digital pedal that controls the volume or amp/effect parameters on Mustang" GT, III, IV and V amplifiers and on Mustang Floor multi-effects unit. Switch between "Volume" and "Expression" modes by stepping on the toe-end of the pedal. Red and green LEDs indicate the mode in use. The Volume mode-indicated by an illuminated green LED-controls the master volume or can be turned off. The Expression mode-indicated by illumination of the red LED-controls most Mustang amp and effects parameters, such as frequency and modulation effects.