Vowel Content Influences Relative Pitch Perception in Vocal Melodies

Note-to-note changes in brightness are able to influence the perception of interval size. Changes that are congruent with pitch tend to expand interval size, whereas changes that are incongruent tend to contract. In the case of singing, brightness of notes can vary as a function of vowel content. In the present study, we investigated whether note-to-note changes in brightness arising from vowel content influence perception of relative pitch. In Experiment 1, three-note sequences were synthesized so that they varied with regard to the brightness of vowels from note to note. As expected, brightness influenced judgments of interval size. Changes in brightness that were congruent with changes in pitch led to an expansion of perceived interval size. A follow-up experiment confirmed that the results of Experiment 1 were not due to pitch distortions. In Experiment 2, the final note of three-note sequences was removed, and participants were asked to make speeded judgments of the pitch contour. An analysis of response times revealed that brightness of vowels influenced contour judgments. Changes in brightness that were congruent with changes in pitch led to faster response times than did incongruent changes. These findings show that the brightness of vowels yields an extra-pitch influence on the perception of relative pitch in song.