Tonal Description of Music Audio Signals

Emilia Gómez
University Pompeu Fabra, Barcelona, Spain (July, 2006)


In this doctoral dissertation we propose and evaluate a computational approach for the automatic description of tonal aspects of music from the analysis of polyphonic audio signals. The problems that appear when computer programs try to automatically extract tonal descriptors from musical audio signals are also discussed.

We propose a number of algorithms to directly process digital audio recordings from acoustical music in order to extract tonal descriptors. These algorithms focus on the computation of pitch class distributions descriptors, the estimation of the key of a piece, the visualization of the evolution of its tonal center or the measurement of the similarity between two different musical pieces. Those algorithms have been validated and evaluated in a quantitative way. First, we have evaluated low-level descriptors and their independence with respect to timbre, dynamics and other external factors to tonal characteristics. Second, we have evaluated the method for key finding, obtaining an accuracy around 80% for a music collection of 1400 pieces with different characteristics. We have studied the influence of different aspects such as the employed tonal model, the advantage of using a cognition-inspired model vs machine learning methods, the location of the tonality within a musical piece, and the influence of the musical genre on the definition of a tonal center. Third, we have proposed the extracted features as a tonal representation of an audio signal, useful to measure similarity between two pieces and to establish the structure of a musical piece.

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