Patent ID: 7534951

Claim:
A rhythm tracking apparatus comprising: beat extraction means for detecting a change in a portion of a power spectrum in a spectrogram of an input music signal, the change having a magnitude greatest among other changes determined for adjacent portions of the power spectrum, and for outputting a detection output signal that is synchronized in time to the changing portion in synchronization with the input music signal; tempo value estimation means for detecting a self-correlation of the detection output signal from the beat extraction means and for estimating a tempo value of the input music signal; a variable frequency oscillator in which an oscillation center frequency is determined on the basis of the tempo value from the tempo value estimation means and a phase of an output oscillation signal is controlled on the basis of a phase control signal; phase comparison means for comparing the phase of the output oscillation signal from the variable frequency oscillator with the phase of the detection output signal of the beat extraction means and for supplying a resultant comparison error signal as the phase control signal to the variable frequency oscillator; and output means for generating and outputting a beat synchronization signal synchronized with the beat of the input music signal on the basis of the output oscillation signal of the variable frequency oscillator.