The GK-2a is a hexaphonic pickup designed to drive Roland guitar synths. It consists of six tiny pickups (one for each guitar string) and sends six parallel analogue signals to an apropriate receiver, using the 13 pin 'GK' cable. The GK-2a is often refered to as a 'MIDI pickup' - this is partialy true, as it does transmit patch-change and volume-control MIDI signals. However, the guitar signal itself is analogue, NOT MIDI; it requires an external processing unit to be converted to MIDI.