An audio control system including a unique pulley assembly for automated linear movement of the device is disclosed. The pulley assembly includes two pulleys with two different diameters and parallel axes of rotation. A capstan with a different axis of rotation than either of the pulleys is disposed between the two pulleys. A string is wound around the capstan and the circumferences of the pulleys. The diameters of the pulleys are selected such that the turns of the string on the pulley do not overlap.
