Electro-Harmonix DUAL EXPRESSION Expression PedalThe Electro Harmonix Dual Expression pedal is designed to provide external control over two applicable effects at once. Say you have a flanger pedal whose speed parameter could be controlled by one expression pedal, and whose modulation rate could be controlled with another; if that were the case, you could use this Electro Harmonix product to control both of those parameters at the same time, with some degree of independence. The Dual Expression