First display object associated with a control operating member and a second display object associated with a tone color effect parameter are displayed, and variation of a displayed position of the first display object is controlled in accordance with operation of the control operating member. Control value of the tone color effect parameter is determined in response to variation in relationship between the first and second display objects, and tone control is performed on the basis of the determined control value. Further, the variation of the displayed position of the first display object is controlled so as to move on and along a set path, so that displayable positions of the first display object is limited to the set path. Control value of the tone color effect parameter is determined on the basis of relationship between displayed position of the first and second display objects to perform tone control.