initialise, make sure apc is off, and adjust the reverb to taste.
set panel memory 1 to -12 in the keyshift, panel memory 2 to normal, and panel memory 3 to +12 in the keyshift.
set footswitch 1 to panel memory decrement and footswitch 2 to panel memory increment.
if you want sustain too, get an FC2 multifootswitch.
alternatively use right 1 and right 2 to shift octaves, carefully adjusting balance and pan so you cannot hear the difference between them, with apc and left off.