Tonal Pitch Step Distance: a Similarity Measure for Chord Progressions

The computational analysis of musical harmony has received a lot of attention the last decades. Although it is widely recognized that extracting symbolic chord labels from music yields useful abstractions, and the number of chord labeling algorithms for symbolic and audio data is steadily growing, surprisingly little effort has been put into comparing sequences of chord labels. This study presents and tests a new distance function that measures the difference between chord progressions. The presented distance function is based on Lerdahl’s Tonal Pitch Space [10]. It compares the harmonic changes of two sequences of chord labels over time. This distance, named the Tonal Pitch Step Distance (TPSD), is shown to be effective for retrieving similar jazz standards found in the Real Book [3]. The TPSD matches the human intuitions about harmonic similarity which is demonstrated on a set of blues variations.