The Effects of Timbre on Perceptual Grouping in Melodic Sequences

Previous research has determined that timbre manipulations influence pitch perception in intervals (e.g., Russo & Thompson, Citation2005), as well as within brief (for example, interleaved) tone sequences (e.g., Creel, et al., Citation2004). The current investigation evaluated whether the effects of timbre on pitch-related judgments could also extend to the perceived phrase structure in a complex melody. Participants listened to six-tone melodic sequences, each of which were followed by a target tone that either retained the same (static) timbre, or had been low- or high-pass filtered to produce a dull or bright timbre, respectively. In each timbre condition the pitch change to the target constituted either an ascending or descending interval of a 3rd (2 scale steps), perfect 4th (3 scale steps), or a 6th (5 scale steps), with equal probability. Participants rated how well the target continued the melody. Contrary to hypotheses, participants rated targets as poor continuances of the melody if any timbre shift occurred, regardless of interval size. This suggests that timbre’s influence was not subsumed by high-order melodic processing. This effect negatively correlated with musical training. As expected, larger intervals were less likely to be perceived as belonging to the initial melody, indicating that participants used expectations about pitch intervals to make judgments. Taken together, these findings reveal that, at least under conditions reflecting a single change in instrument source, timbre can impact the perception of melodic phrase structure.