To accurately extract a tempo without being influenced by a peak detection error which is likely to occur on a sampled voice data.

Two or more peaks are detected from the sampled voice data of an arbitrary musical piece (Step S14). Based on a 1st peak train before movement located in a line according to the peak generation time of these two or more detected peaks, and a 2nd peak train after the peak generation time of the 1st peak train are moved by a prescribed time (t), a distance function between peaks used as a function of the time (t) is calculated (Step S16) which is the total sum of time between respectively nearest peaks between the 1st peak train and the 2nd peak train. Since this distance function between peaks changes periodically according to the periodicity of intervals of the 1st peak train, the tempo of the arbitrary musical piece is calculated based on the cycle of the distance function between peaks (Step S18).

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