Oct1 knob: Adjust the volume of the first voice of octave. 
Oct2 knob: Adjust the volume of the second voice of octave. 
Dry knob: Adjust the volume of dry signal. 
Mode switch: Switch between top(+1 OCT and +2 OCT), both(-1 OCT and +1 OCT) and bottom(-1 OCT and -2 OCT) mode.