The Avoidance of Part-Crossing in Polyphonic Music: Perceptual Evidence and Musical Practice

Abstract

A number of experimental studies have demonstrated that the perceptual tracking of auditory streams is confounded when streams cross with respect to pitch. A study of part-crossing in 105 polyphonic works by J. S. Bach shows a marked reluctance to have parts cross—even when the effects of pitch distribution (tessitura) are controlled. Moreover, when the textural density increases beyond two concurrent voices, Bach becomes more vigilant to avoid part-crossing even though an increase in part- crossing is preordained. In light of evidence that perceptual confusion increases with the number of concurrent voices, these results are consistent with the hypothesis that Bach endeavors to minimize perceptual confusion as the density of auditory images increases.