Timbre perception and auditory grouping principles can provide a theoretical basis for aspects of orchestration. In Experiment 1, 36 excerpts contained two streams and 12 contained one stream as determined by music analysts. Streams—the perceptual connecting of successive events—comprised either single instruments or blended combinations of instruments from the same or different families. Musicians and nonmusicians rated the degree of segregation perceived in the excerpts. Heterogeneous instrument combinations between streams yielded greater segregation than did homogeneous ones. Experiment 2 presented the individual streams from each two-stream excerpt. Blend ratings on isolated individual streams from the two-stream excerpts did not predict global segregation between streams. In Experiment 3, Experiment 1 excerpts were reorchestrated with only string instruments to determine the relative contribution of timbre to segregation beyond other musical cues. Decreasing timbral differences reduced segregation ratings. Acoustic and score-based descriptors were extracted from the recordings and scores, respectively, to statistically quantify the factors involved in these effects. Instrument family, part crossing, consonance, spectral factors related to timbre, and onset synchrony all played a role, providing evidence of how timbral differences enhance segregation in orchestral music.

This study uses a corpus of excerpts from eighteenth- and early nineteenth-century string quartets to examine how four acoustic cues—onset and offset synchrony, pitch comodulation, and spectral overlap—help to afford the perception of auditory streams. Two types of streams are dealt with: textural streams , which house individual string parts or groups of them that function as single musical units; and music streams , which typically house the music as a whole and distinguish it from other simultaneous sounds of music. The corpus contained real excerpts from classical string quartets as well as synthesized excerpts in which lines from two different quartets were combined. Both the author and ten survey respondents analyzed the corpus, identifying likely textural streams. Each of the four acoustic cues was modeled computationally, in order to assess its prevalence in textural and music streams found in the corpus. The results suggested that some cues are more important than others in establishing textural streams, music streams, or both.

The aim of this study was to examine the effects of three acoustic parameters on the difficulty of segregating a simple 4-note melody from a background of interleaved distractor notes. Melody segregation difficulty ratings were recorded while three acoustic parameters of the distractor notes were varied separately: intensity, temporal envelope, and spectral envelope. Statistical analyses revealed a significant effect of music training on difficulty rating judgments. For participants with music training, loudness was the most efficient perceptual cue, and no difference was found between the dimensions of timbre influenced by temporal and spectral envelope. For the group of listeners with less music training, both loudness and spectral envelope were the most efficient cues. We speculate that the difference between musicians and nonmusicians may be due to differences in processing the stimuli: musicians may process harmonic sound sequences using brain networks specialized for music, whereas nonmusicians may use speech networks.