A beat density detecting apparatus and an information playback apparatus are provided to detect distinctive characteristics that music or the like has and to provide the same as a novel information volume. Playback data read out from an information recording medium, such as an optical disc, and sub-code data containing the information of an elapsed track time indicating a recording position of the playback data are provided to a beat detecting unit and a beat position detecting unit, respectively. The beat detecting unit detects the number of occurrences of a change in amplitude at each predetermined frequency of the playback data, and the beat position detecting unit detects an elapsed track time from the sub-code data. Further, a beat density computing unit finds the number of occurrences with respect to the elapsed track time as the characteristics information of a beat density. By displaying the characteristics information of the beat density on a display unit in a way that the user or the like can visually recognize, it is possible to provide the distinctive characteristics that music or the like has not as instantaneous characteristics, but as the characteristics of a relatively long period, or the whole of the characteristics of a signal subject to audio playback.