Spectro-temporal factors in the perceptual segregation of tonal sequences

Abstract

Spectral factors such as differences in harmonic content are powerful cues in the organization of tonal sequences. Temporal factors such as rise time, however, have been shown to be poor cues [W. M. Hartmann and D. Johnson, Mus. Perc. 9(2), 155–184 (1991)]. The relative salience of these factors was investigated further using complex tones sequenced in a repeating ABA-‘‘gallop’’ format, under conditions in which tones A and B had the same, or different harmonic content and/or temporal envelope shape. The F0 difference between A and B was initially 0 Hz, but increased over the course of a trial, until terminated by a listener, indicating perceptual segregation of the input sequence into sub-sequences comprising A and B tones, respectively. The F0 difference required to reach this segregation threshold provided a measure of the efficacy of stimulus features of A and B as cues for sequential organization. Sequences combining differences in spectral content and temporal envelope shape required the smallest F0 change for segregation. Sequences of tones with the same harmonic structure and temporal envelope required the largest F0 changes, while the other conditions fell in the middle of this range. Results will be discussed in terms of implications for sequential organization as well as for the perception of timbre. [Work supported by NSERC, Canada.]