In this paper we propose a technique based on the phase evolution of the Short Time Fourier Transform (STFT) for increasing the spectral resolution in the time-frequency analysis of a musical signal. It is well known that the phase evolution of the STFT coefficients brings important information on the spectral components of the analysed signal. This property has already been exploited in different ways to improve the accuracy in the estimation of the frequency of a single component. In this paper we propose a different approach, where all the coefficients of the STFT are used jointly to build a measure of how likely all the frequency components are, in terms of their phase coherence evaluated in consecutive analysis window. In more detail, we construct a phase coherence function which is then integrated with the usual amplitude spectrum to obtain a refined description of the spectral components of an audio signal.

Download

In this paper, a novel approach for the computation of a pitch salience function is presented. The aim of a pitch (considered here as synonym for fundamental frequency) salience function is to estimate the relevance of the most salient musical pitches that are present in a certain audio excerpt. Such a function is used in numerous Music Information Retrieval (MIR) tasks such as pitch, multiple-pitch estimation, melody extraction and audio features computation (such as chroma or Pitch Class Profiles). In order to compute the salience of a pitch candidate f , the classical approach uses the weighted sum of the energy of the short time spectrum at its integer multiples frequencies hf . In the present work, we propose a different approach which does not rely on energy but only on frequency location. For this, we first estimate the peaks of the short time spectrum. From the frequency location of these peaks, we evaluate the likelihood that each peak is an harmonic of a given fundamental frequency. The specificity of our method is to use as likelihood the deviation of the harmonic frequency locations from the pitch locations of the equal tempered scale. This is used to create a theoretical sequence of deviations which is then compared to an observed one. The proposed method is then evaluated for a task of multiple-pitch estimation using the MAPS test-set.

Download