In a mixer system having a digital mixer having functions of processing an audio signal in an input channel and outputting the signal via an ST bus, and a PC executing a DAW application realizing a function of plural tracks to record waveform data, a WET button corresponding to the input channel is provided to the digital mixer to select a DRY mode for inputting signal which is inputted from outside the device to the input channel, to the ST bus without sending the signal to the DAW application, or a WET mode for inputting signal which are inputted from outside the device to input channel, to the ST bus after sending the signal to the DAW application for processing and being sent back to the digital mixer, in response to a pressing of the WET button.