To provide an audio signal processing apparatus, an audio signal processing system, and an audio signal processing method that include: a first converting part that converts an input data sequence of an audio signal into frequency data using an IIR system DFT at each processing timing, a window processing part that performs window processing on the frequency data using a window function, a signal processing part that performs predetermined signal processing on the frequency data on which window processing has been performed, and a second converting part that converts the frequency data, on which the signal processing has been performed, into a time-axis data sequence.