By user's pinching operation on a slider 2e of a controller 2, it is judged that the slider 2e has been operated on two points, so that a DAW screen is zoomed in or out in accordance with the speed at which the distance between the two points has changed and the amount by which the distance between the two points has changed. By user's sliding operation on the slider 2e of the controller 2, it is judged that the slider 2e has been operated on one point, so that the function of the DAW is controlled in accordance with the speed at which the slider 2e has moved and the amount by which the slider 2e has moved.