Commentary on Shaffer et al.: A cluster analysis of harmony in the McGill Billboard dataset

This short commentary on the target paper by "A cluster analysis of harmony in the McGill Billboard" by Shaffer et al. starts with observing that not all harmonic progressions that are theoretically possible are equally common. Instead, some progressions are more popular than others in popular. In fact, certain harmonic progressions are closely associated with specific styles and sub-genres and it is the aim of the target paper to provide a meaningful classification system for harmonic progression. The commentary identifies several strengths of the target paper, including a nice balance between rigorous empirical work and providing a context and interpretations that are musicologically well-informed. In its critique the commentary points to the limitations of only using harmonic bigrams (i.e. the transitions between two chords) as the empirical data and the missing link to related literature on harmonic modelling in the music information retrieval community.