I would like to create a "volume pedal" for my synthesizer that uses a knob instead of a foot pedal. What do I need to make this? I assume I need an audio taper stereo potentiometer, but which value? I would like 1/4" mono ins and outs for the R and L channels to use in front of stereo effect pedals. Any advice or direction appreciated! The purpose is to create volume swells similar to what's done with a guitar and volume pedal. I can do it with the volume knob on my synth, but would prefer to have an external knob to do this.