Perception of multiple pitches: Sequential and simultaneous pitch relationships

The perception of pitch, a dimension of sound that is important for music perception, speech perception, and sound source segregation, is influenced by its context, both sequential and simultaneous. In music, pitch sequences form melodic contours, and simultaneous pitches form chords and harmony. A series of experiments investigated the perception of melodic contour in pitch as well as two other auditory dimensions, brightness and loudness. The results showed that subjective ratings of continuation for brightness and loudness sequences conformed to the same general contour-based expectations as pitch sequences, suggesting that melodic expectations are not unique to the dimension of pitch. Listeners with congenital amusia, however, exhibited less impairment on a short-term memory task for loudness contours than for pitch contours, suggesting a pitch-specific deficit. In a pair of experiments, priming of a familiar tonal context improved accuracy on a pitch interval discrimination task. However, the overall benefit to performance from tonal context was small, suggesting that previously reported effects of response time may mainly reflect expectancy as opposed to perceptual accuracy. In the last series of experiments, listeners accurately identified pitches in mixtures of three concurrent complex tones, despite poor peripheral resolvability. These stimuli help to dissociate two normally confounded variables in complex pitch, harmonic number and peripheral resolvability. The results were compared with outputs from two kinds of auditory models, one based on the rate-place code for pitch and the other based on the temporal code. Overall, these findings suggest that pitch perception involves bottom-up integration of both spectral and temporal information, as well as top-down effects of learning and context.