Invariance of edit-distance to tempo in rhythm similarity

Despite the long history of music psychology, rhythm similarity perception remains largely unexplored. Several studies suggest that edit-distance-the minimum number of notational changes required to transform one rhythm into another-predicts similarity judgments. However, the ecological validity of edit-distance remains elusive. We investigated whether the edit-distance model can predict perceptual similarity between rhythms that also differed in a fundamental characteristic of music-tempo. Eighteen participants rated the similarity between a series of rhythms presented in a pairwise fashion. The edit-distance of these rhythms varied from 1 to 4, and tempo was set at either 90 or 150 beats per minute (BPM). A test of congruence among distance matrices (CADM) indicated significant inter-participant reliability of ratings, and non-metric multidimensional scaling (nMDS) visualized that the ratings were clustered based upon both tempo and whether rhythms shared an identical onset pattern, a novel effect we termed rhythm primacy. Finally, Mantel tests revealed significant correlations of edit-distance with similarity ratings on both within- and between-tempo rhythms. Our findings corroborated that the edit-distance predicts rhythm similarity and demonstrated that the edit-distance accounts for similarity of rhythms that are markedly different in tempo. This suggests that rhythmic gestalt is invariant to differences in tempo.