Patent ID: 8309834

Claim:
A computer-implemented method of detecting a chord in an audio signal, comprising: converting a first portion of the audio signal from a time domain to a first frequency domain portion; detecting in the frequency domain portion a peak at a first fundamental frequency and three peaks, each peak at an integer-interval harmonic frequency of the first fundamental frequency; detecting in the frequency domain portion a peak at a second fundamental frequency and three peaks, each peak at an integer-interval harmonic frequency of the second fundamental frequency; detecting in the frequency domain portion a peak at a third fundamental frequency and three peaks, each peak at integer-interval harmonic frequencies of the third fundamental frequency; converting a second portion of the audio signal to a second frequency domain portion; determining the existence of a first note by detecting in the second frequency domain portion of the audio signal a peak at the first fundamental frequency and one peak at an integer-interval harmonic frequency of the first fundamental frequency; determining the existence of a second note by detecting in the second frequency domain portion of the audio signal a peak at the second fundamental frequency and one peak at an integer-interval harmonic frequency of the second fundamental frequency; determining the existence of a third note by detecting in the second frequency domain portion of the audio signal a peak at the third fundamental frequency and one peak at an integer-interval harmonic frequency of the third fundamental frequency; storing in a computer memory an indication of the existence of the first, second and third notes; and outputting to a user a visual representation indicating the presence of the chord in the audio signal portion when the indication is stored in the memory.