An audio signal processor is composed of a data path unit, a mode register and a state machine unit. The data path unit applies one or more arithmetical operation to an audio signal for performing signal processing of the audio signal. The mode register stores mode information specifying the signal processing to be performed by the data path unit. The state machine unit sequentially feeds control signals according to the mode information for enabling the data path unit to apply one or more arithmetical operation to the audio signal so as to perform the signal processing. The performed signal processing is composed of the one or more arithmetical operations, and is specified by the mode information stored in the mode register.