Abstract: An automatic guitar string tuning device includes a foot-operated switch for controlling an electrical solenoid which rotates a cam shaft mounted upon a guitar or other stringed instrument. The solenoid rotates the cam shaft between first and second positions under the control of the foot switch. Several of the guitar strings are secured to tensioning arms which engage corresponding camming surfaces formed upon the rotating shaft. Rotation of the cam shaft between the first and second positions causes movement of the tensioning arms and thereby changes the pitch of the strings attached thereto.