Vocoding is the process of using a “carrier” signal to create synthesized speech and singing.
You can use your guitar to guide all sorts of robot, synthesizer and tuning effects.
Troy Sanders of Mastodon uses the VoiceTone Synth in his live performances.
For more information about VoiceTone Synth click here:VoiceTone Synth
To read more about Vocoding see: Wikipedia Vocoder