Music--Acoustics and physics

The convention of representing pitch distances within a circular symmetric scheme has a long history. Perception of the pitch pattern of pairs of circular tones (Shepard, 1964) was examined in three different orderings of the comparison tone. Consistent with previous reports, when tone pairs were randomized the pitch was equally likely to be judged as ascending or descending as the frequency change neared the half-octave. In the ordered conditions, the pitch boundary was sensitive to the direction of frequency change such that hysteresis effects were observed for all subjects. A matrix was constructed of directional pitch judgments to all pairs of circular tones presented randomly. Perception of selected pairs was then predicted on the basis of map region consistency. The results indicate that perception of pitch change is influenced not only by the frequency difference between members of a pair, but also by preceding percepts.