The vBow, a virtual violin bow musical controller, has been designed to provide the computer musician with most of the gestural freedom of a bow on a violin string. Four cable and servomotor systems allow for four degrees of freedom, including the lateral motion of a bow stroke across a string, the rotational motion of a bow crossing strings, the vertical motion of a bow approaching and pushing into a string, and the longitudinal motion of a bow travelling along the length of a string. Encoders, attached to the shaft of the servomotors, sense the gesture of the performer, through the rotation of the servomotor shafts, turned by the motion of the cables. The data from each encoder is mapped to a parameter in synthesis software of a bowed-string physical model. The software also sends control voltages to the servomotors, engaging them and the cables attached to them with a haptic feedback simulation of friction, vibration, detents and elasticity.