In an audio signal processing apparatus for recording a plurality of kinds or systems of audio signals on a recording medium and for reproducing a plurality of kinds or systems of audio signals recorded on the recording medium, in a state where a mixing output mode of mixing the plurality of kinds or systems of audio signals and outputting the mixed audio signals is designated, (i) when a recording operation mode of recording the plurality of kinds or systems of audio signals on the recording medium is designated, the plurality of kinds or systems of audio signals are mixed and outputted while making levels of the plurality of kinds or systems of audio signals equal to each other, and (ii) when a reproducing operation mode of reproducing a plurality of kinds or systems of audio signals recorded on the recording medium is designated, the plurality of kinds or systems of audio signals reproduced from the recording medium are mixed and outputted according to an arbitrarily variable mixing ratio. Thus, the audio signal processing apparatus can record the plurality of kinds or systems of audio signals, effectively utilizing the dynamic range of the recording medium, and can mix and reproduce the plurality of kinds or systems of audio signals in a good reproduction state where S/N is good.