Combining Musicological Knowledge About Chords and Keys in a Simultaneous Chord and Local Key Estimation System

Abstract

In this paper, we present a probabilistic framework for the simultaneous estimation of chords and keys from audio. The framework is formulated in terms of acoustic models for both keys and chords, and a prior model that contains musicological knowledge about chords and keys. The latter consists of a compound of four components: a duration and a change model for both keys and chords. This division allows us to modify each of the components separately and to choose the most appropriate sources of knowledge for each of them. Furthermore, this makes it easier to interpret their role and their relevance in the estimation procedure. We compared multiple configurations of our system, increasing in complexity. This has permitted us to explore the relation between keys and chords, and the importance of integrating prior musicological knowledge into an automatic estimation system. It was found that chord estimation scores mostly depend on the integration of durational knowledge, while key estimation also requires prior information about the broader context.