In a digital mixer, a standard mode or a switched mode of an input patch is selectable. When shifting from the standard mode to the switched mode is selected, input port information in input patch data stored in a current memory is converted according to a port correspondence relation indicated by conversion data. When shifting from the switched mode to the standard mode is selected, the input port information in the input patch data stored in the current memory is reversely converted to original information according to the port correspondence relation indicated by the conversion data.