Octave Equivalence: Difficult to Perceive, But Improvements Are Possible With Training

Musical notes separated by exactly one or more octaves share similarities and, in some respects, might be treated as interchangeable. This octave equivalence is sometimes evident, but in many contexts, is very hard to hear. In two large experiments, participants were asked to judge the similarity of tone pairs, presented sequentially, before and after octave equivalence training. Contrary to some prior research on the topic, it was clearly explained what sort of "similarity" they should rate tone pairs on (i.e., octave equivalence). Each pair consisted of either two tones of the same pitch class but separated by one or more octaves, or two tones of adjacent pitch classes also separated by one or more octaves (±1 semitone). Coherent with past work, this task was difficult. However, both musician and nonmusician samples scored above chance in this task at pretest. Also interestingly, performance improved after training. During the training task, participants also heard pairs of tones but were given the correct response to facilitate learning. Pretest performance and improvements for both groups were not substantial, however, again illustrating the difficulty of hearing octave equivalence, depending on the exact context. Potential relationships to relative and absolute pitch are also briefly discussed.