Pitch perception in changing harmony.

摘要

The role of harmony in the definition of tonality provides theoretical framework for the hypothesis that harmonic context affects pitch perception. In tonal music, the stability of individual notes depends on the harmonic setting. It seems then reasonable to expect harmonically guided variations in the cognitive representation of tones. With the purpose of enhancing current models of pitch perception, this thesis proposes an empirical investigation of the effects of harmony on pitch sensitivity. In two experiments, nonmusicians performed a same/different discrimination task on two pitches (a reference tone RT and a comparison tone CT) that were embedded in a melody with a clearly implied harmony. Visual cues facilitated the identification of the tones. The main experiment included only stimuli with different harmonic contexts for RT and CT. It consisted of a repeated-measures design with two bi-level factors, pitch (RT=CT and RT≠CT) and harmonic stability (equal and unequal stability for CT with respect to RT). By considering only changing-harmony stimuli, this study greatly minimized effects of potential confounds, allowing a comparative examination of the perception of equal versus different pitches. An ANOVA with percent correct as dependent variable and c (response-bias measure) as covariate revealed greater disruption in discrimination of different than identical notes; better pitch sensitivity in unequal than equal harmonic-stability situations; and increased perception abilities for unequally, with respect to equally, stable notes that differed in pitch, but the opposite effect for equal tones. The second experiment consisted of a between-subjects design with two factors, harmony (changing and nonchanging) and pitch (as above). An ANOVA showed better pitch discrimination abilities (d') under nonchanging than changing harmonic contexts in common musical situations. Altogether, the findings suggest that changing harmonic settings tend to bring together the percepts of pitches that are introduced in adjacent chordal functions, particularly when the tones are stable members of their contextual harmony. This thesis contributes to the field of music cognition by illuminating our understanding of the perceptual mechanisms involved in the interaction of pitch and harmony, proposing an alternative methodological approach, and emphasizing the problems that underlie the study of contextual aspects of music.