An audio signal processing apparatus includes a high-pass filter for extracting from an audio signal a frequency component higher than f0, n band-pass filters for extracting, from the audio signal, frequency components falling within a frequency range from f0 / N to f1 / N, n harmonic overtone generators for frequency multiplying each of outputs of the n band-pass filters by N, a first combining unit for combining the generated harmonic overtone components, a level detector for detecting a level of a supplied harmonic overtone component, a gain controller for controlling dynamically the harmonic overtone component supplied from the first combining unit, and a second combining unit for combining the frequency component extracted by the high-pass filter and a harmonic overtone component output from the gain controller, where N is (n being a natural number), f0 is a first predetermined frequency, and f1 is a second predetermined frequency higher than f0.