A synthesizer that uses a guitar, rather than a keyboard, as its controlling interface. Guitar controllers can be divided into two categories, those that use a conventional guitar with pitch converters detecting the notes played, and those that directly detect the hand motions of the player with touch pads and sensors. (The latter type generally produce no sound of their own, and often bear little resemblance to a conventional guitar.) Guitar synthesizers have always proven difficult to design and have often disappointed both their makers and their users; design of the pitch converters for systems that use conventional guitars has proven to be hugely problematic. (Development costs of the Avatar, one of the first guitar synths, are reputed to be what put the ARP Instruments synthesizer com