Reassigned spectrum-based feature extraction for GMM-based automatic chord recognition

Most existing automatic chord recognition systems use a chromagram in front-end processing and some sort of classifier (e.g., hidden Markov model, Gaussian mixture model (GMM), support vector machine, or other template matching technique). The vast majority of front-end algorithms derive acoustic features based on a standard short-time Fourier analysis and on mapping energy from the power spectrum, or from a constant-Q spectrum, to chroma bins. However, the accuracy of the resulting spectral representation is a crucial issue. In fact, conventional methods based on short-time Fourier analysis involve an intrinsic trade-off between time resolution and frequency resolution. This work investigates an alternative feature set based on time-frequency reassignment, which was applied in the past to speech processing tasks such as formant extraction. As shown in the following experiments, the reassigned spectrum provides a very accurate front-end for the GMM-based chord recognition system here investigated.