Check out this cool DIY servo electric guitar. I am not a guitar expert here but this thing is cool!
A servoelectric guitar is a fretless guitar that is played by controlling servomotors that change the tension of the strings over an octave or more on a real-time basis. Tuning is maintained by closed loop tension feedback for rapid and predictable response. Relatively small electrical motors and DC servo amplifiers are possible through a novel compensator spring design.