1. Data processing apparatus comprising: (i) an array of user-operable controls, said controls being adjustable by movement of a user's hand while touching a control; (ii) a detector for detecting when a user's hand is touching a control; (iii) a display screen for displaying respective screen icons associated with said controls; and (iv) a display processor, responsive to a detection that a user's hand is touching one of said controls, for altering said screen icon associated with that control.