In a PC that controls a mixer engine having a programmable DSP, any object such as a knob or the like is enabled to be duplicated from a control screen corresponding to various signal processing components and disposed at any position on a user control screen to make it possible to use the user control screen as a control screen editable by a user. When an object such as a knob is designated in the user control screen and a predetermined direction is issued, a menu is displayed on a display. Then, when “Open Original” is selected from the menu, it is understood that display of the control screen including an original of the designated object is directed, and the control screen is displayed on the display.