The GR55 includes both MIDI In and Out sockets. Although the synth sounds can’t be played via MIDI, the MIDI-interfacing capabilities make it easy to use the GR55 as a controller to drive soft synths from the guitar. However, it’s important to note that Roland have developed their own system of triggering the internal synthesizer sounds that follows picking dynamics, strumming, string bending and so on. While many of these aspects of performance translate fairly well to MIDI, you may still find that the internal sounds respond better to normal guitar-playing techniques than do externally triggered sounds.