HMM-based approach for automatic chord detection using refined acoustic features

We discuss an HMM-based method for detecting the chord sequence from musical acoustic signals using percussion-suppressed, Fourier-transformed chroma and delta-chroma features. To reduce the interference often caused by percussive sounds in popular music, we use Harmonic/Percussive Sound Separation (HPSS) technique to suppress percussive sounds and to emphasize harmonic sound components. We also use the Fourier transform of chroma to approximately diagonalize the covariance matrix of feature parameters so as to reduce the number of model parameters without degrading performance. It is shown that HMM with the new features yields higher recognition rates (the best in MIREX 2008 audio chord detection task) than that with conventional features.