| 摘要 |
A time fraction or short duration of a musical sound wave is first analyzed by the FFT processing into frequency components in the form of a frequency spectrum having a number of peak energy levels, a predetermined frequency range (e.g. 63.5-2032 Hz) of the spectrum is cut out for the analysis of chord recognition, the cut-out frequency spectrum is then folded on an octave span basis to enhance spectrum peaks within a musical octave span, the frequency axis is adjusted by an amount of difference between the reference tone pitch as defined by the peak frequency positions of the analyzed spectrum and the reference tone pitch used in the processing system, and then a chord is determined from the locations of those peaks in the established octave spectrum by pattern comparison with the reference frequency component patterns of the respective chord types. Thus, the musical chords included in a musical performance are recognized from the sound wave of the musical performance. Autocorrelation method may preferably be utilized to take the autocorrelation among the frequency components in the octave profile on the basic unit of a semitone span in order to enhance the peaks in the frequency spectrum of the octave profile on a semitone basis.
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