The present invention provides a human-machine interface where control is achieved without the use of buttons. By providing multiple knobs, the audio system maximizes functionality while minimizing cost and space requirements. Each knob is capable of two selection modes: a first selection mode provided by rotating the knob and a second selection mode provided by depressing the knob. The two selection modes correspond to ergonomic selection pairs for controlling the audio system. The reduced area required for controls allows for a larger display area; which provides the user with a more attractive display that can convey more information. When a change in a status, through knob manipulation is sensed by the audio system, the display automatically provides a menu that corresponds to the ergonomic pair assigned to that knob. The automated switching of menus minimizes navigation between screens, while providing full manipulation of that audio system function using a single knob control. The present invention also provides for the display to visually indicate which knob is being used.