Electro-Harmonix SINGLE EXPRESSION Expression PedalThe EHX Performance Series Expression Pedal by Electro Harmonix is designed to provide external control over applicable effects. Say you have a flanger pedal whose speed parameter can be controlled by an expression pedal; if that were the case, you could use this Electro Harmonix product to control that parameter. The EHX Expression Pedal sports a single 1 4" TRS output, as well as a range knob that allows you to tune the width of the pedal's sweep;