Parsing complex rhythmic structures: The contribution of spectral and temporal dimensions of timbre

Abstract

Perceptual parsing of sequences with multiple possible metric interpretations was studied. Sequences of 12 complex tones were used as stimuli, with either no deliberate accents provided, or physical accents introduced by changing timbre at positions implying a triple, quadruple, or multiple meter (i.e., both triple and quadruple simultaneously). Subjects reported if they perceived a triple meter, quadruple meter, ambiguous meter, or no meter. The number of harmonics (2, 4, or 8) or the locus of three harmonics were the spectral variables used to mark timbre accents. Steepness of rise and decay time (95+5 ms versus 5+95 ms) was the temporal variable used. These attributes served well as accent markers for sequences with unambiguous meters. However, listeners were generally unable to parse sequences where multiple meters were provided by the same timbre cue. For sequences where multiple meters were provided by contrasting timbres, listeners generally picked the metrical structure implied by spectrally richer or brighter timbres comprising more or higher harmonics. Temporal envelope slope was not effective in facilitating parsing of meters.