Abstract: A rotary control for a music mixing desk consists of a cylindrical knob which includes an information display. The knob is fashioned from an electrically conductive plastic material and is in electrical contact with the spindle of the knob which is connected to a touch sensitive circuit. The rotary control is thereby able to sense the touch of a mixing desk operator without the operator having to turn the knob. The mixing desk can be programmed to undertake various actions upon touching the knob. The display consists of a plurality of light transmitting channels composed of an optic fiber or a wave guide comprising a bundle of optic fibers. Light transmitting elements are disposed at one end of respective channels and circuitry connected to the elements enable certain selected elements to be activated to denote certain conditions. In this way display of signal conditions can be made within a restricted space.