Abstract: Pitch is tracked for a selected source process characterized by a pitch source having many harmonics followed by a bandpass filtering (e.g., human speech or other common processes). The filtering in the original source process causes an original pitch pulse to be seen in somewhat modified form and followed by ringing at band pass filter frequencies. Often, the ringing produces peaks of unpredictable amplitude, a characteristic making it difficult to use simplistic methods such as picking waveform amplitude peaks. The method of the present invention avoids such difficulties by taking into account relative phase of harmonics associated with the basic pitch rate or frequency (F0). Since the bandpass filters in the original process produce ringing in frequencies other than the original fundamental frequency, the instantaneous phase of each of the ringing frequencies are only temporally aligned or lined up well for the duration of the original pitch pulse (i.e.