OC-20G Poly Octave

Octave Generator/Distortion (For GK divided pickups)

World’s first polyphonic octave pedal for use with GK-equipped guitars
Octaves can be assigned to different strings for simulated guitar/bass combos
Onboard electric and acoustic guitar simulations, plus Distortion effect
Accommodates playing chords while using octaves
Rugged, dual-pedal design with simple, knob-based controls
*Note that optional GK-2AH pickup or equivalent required for use.

https://www.boss.info/us/products/oc-20g/