The term guitar synthesiser is usually taken to refer to any of a number of devices that allow a guitar player to access synthesizer capabililties while retaining the playing style of a conventional electric guitar.
Today's guitar synthesizers are direct descendants of originals offered in the 1970s by manufacturers such as Hammond. Early versions included the frequency-to-voltage converter type as well as the guitarorgan - an electric guitar with electronic organ components added - such as that made by Vox.
Roland developed its GK line of hexaphonic or divided pickups that provide a separate analog output for each string and could be mounted onto any guitar for use in a guitar-synth system (as shown). And Fender released their VG Stratocaster that directly integrates the Roland GK-2 hardware as well as its own 3 original single-coil pickups.There have also been guitar-like MIDI controllers.