An apparatus of playing back an audio signal includes storage means for dividing exercise tempos of a user into a plurality of groups and storing digital audio data concerning music pieces, the digital audio data being associated with the plurality of groups; a playback circuit that plays back the digital audio data; detecting means for detecting an exercise tempo of the user; and a control circuit that reads out the digital audio data from the storage means to supply the readout digital audio data to the playback circuit. The control circuit determines which group, among the plurality of groups, the exercise tempo detected by the detecting means belongs to, and reads out the digital audio data concerning a music piece associated with the determined group from the storage means to supply the readout digital audio data to the playback circuit.