In an audio mixer, there are stored a plurality of scene data each including, as a set of data, respective settings of a plurality of types of parameters, and these scene data are displayed on a scene data list shown on a display section. Human operator selects a desired one of the scene data from the scene data list using an increment or decrement switch. Determination is made as to whether any object-of-caution data, such as patch data, is among the plurality of types of parameters included in the selected scene data, and, if so, a caution display window is displayed to caution the human operator about the object-of-caution data.