Abstract: An apparatus for selectively adjusting tone of guitar strings during play includes a base plate defining a foot surface, at least one pedal positioned at a front region of the foot surface and disposed for actuation by vertical movement of a user's foot, and at least one level positioned at a rear region of the foot surface, slidably engaged with the base plate, and disposed for actuation by horizontal movement of the heel of the user's foot. The pedal and lever are attached to the bridge of the guitar by cables. Movement of the pedal or lever causes tension of individual guitar strings to be adjusted.