The Aural Perception of Similarity in Nontraditional Chords Related by Octave Equivalence

The purpose of this study was to determine the aural significance of the octave-equivalence I assumption, which is essential to the notion of “pitch class.” To address this question, the author developed a series of 22 experimental items, each consisting of two pairs of nontraditional chords presented harmonically. The two chords of one of the pairs in each item contained the same pitch classes, with each pitch class in the second chord of that pair in a different octave than it had been in the first chord. The two chords in the other pair did not have identical pitch classes. These chord pairs (A, A1) and (A, B) were constructed so that a given chord (A) would be compared alternately with two other chords (A1 and B). The subjects were to judge which pair sounded more alike. The items included chords ranging in size from three to nine pitches. The number of new pitches in Chord B was also treated as a variable in the experiment.

An Apple IIe, equipped with three ALF MC16 Music Cards, presented a random ordering of the experimental items to each of the 51 music majors and 50 nonmusic majors who completed the experiment. Statistical analysis of the 2, 222 individual item responses demonstrated some evidence of the perception of similarity in chords containing six, seven, and eight pitches. The relative number of new pitches in Chord B did not seem to affect the responses of the subjects. Additionally, the responses of the majors did not differ significantly from those of the nonmajors. There was also a significant tendency for both majors and nonmajors to choose the first pair of chords more frequently than the second pair. This tendency was more pronounced for the majors than for the nonmajors.

Additional data provided by a group of 26 professional musicians supported the results obtained in this study.