The present invention relates in general to a menu controlled audio system, and more specifically to automatically altering a system menu according to the features available to the audio system. 
As a result of improvements in electronics, present-day audio systems incorporate many features and functions associated with different audio sources such as a radio, tape player, or compact disc player, and associated with the processing of the audio signal such as noise reduction, volume, balance, fade, and tone control.  As the number of functions have increased, the number of control buttons on the radio have also increased.  User confusion arises because of a large number of small buttons and labels which are hard to read or decipher. 
Control of the audio system can be simplified by using a select button to scan through the possible functions to be adjusted in conjunction with up and down adjustment buttons to adjust the currently selected function.  The currently selected function is displayed on a control panel so that repeated pressing of the select button scans the entire menu of functions available in the audio system.  After periods of inactivity, the selected function may automatically default to the most frequently used one, such as volume control. 
In manufacturing large quantitites of various models or configurations of automotive audio systems, it is less expensive to employ common electronic chassis and other components in the different models or system configurations.  For example, a single model audio system may be used with either two or four speakers depending on the vehicle in which it is installed.  Thus, while one vehicle may have only a front set of stereo speakers installed, another vehicle may have both front and rear sets of stereo speakers.  A single model audio system is used in either configuration since it would be more expensive to produce separate two and four speaker models. 
One of the selectable functions, when there are front and rear speakers, is the fade function which controls the relative gain between the front and rear sets of speakers.  However, in the two speaker configuration, the user can be confused by the appearance of the fade function on the menu since the function is not really available.  Therefore, the different configurations would at least require a change in programming to avoid confusion with regard to the menu.