The CHOPPER has a unique treadle design which allows a better utilization of space in order to accommodate the control functions in a compact foot-pedal sound effect. In the case of the CHOPPER, the space is required to allow the multiple control functions required to achieve delay (echo) emulation, which is a new and unique sound effect generated by this product. The sound effect is controlled by means of a foot treadle that can uniquely control multiple parameters. The rate at which the foot treadle controls the effect is by means of a specific and unique optical coupling. To enable precise control of the effect, there is a visible read out of the modulation frequency which has not been achieved before in a foot pedal. Further, the modulation frequency can be controlled by a MIDI sync code which is also unique in a foot-pedal format.