Thus, one might hypothesize that certain widespread music compositional practices might originate in basic properties of the auditory system that evolved for auditory-scene analysis. Human music, whether vocal or instrumental, also often consists of several voices or streams that overlap in time, and our perception of such music depends on the basic processes of auditory-scene analysis. In a process termed auditory-scene analysis, the auditory system uses spectral, intensity, location, and timing cues to separate the incoming signal into streams or voices that represent each sounding object ( 1). Typically, the sound sources overlap in time and frequency content. The auditory system evolved to identify and locate streams of sounds in the environment emanating from sources such as vocalizations and environmental sounds. The low-voice superiority effect for encoding timing explains the widespread musical practice of carrying rhythm in bass-ranged instruments and complements previously established high-voice superiority effects for pitch and melody. Results from a biologically plausible model of the auditory periphery suggest that nonlinear cochlear dynamics contribute to the observed effect. A behavioral motor task revealed that tapping synchronization was more influenced by the lower-pitched stream. EEG recordings revealed that mismatch negativity responses were larger for timing deviants of the lower tones, indicating better timing encoding for lower-pitched compared with higher-pitch tones at the level of auditory cortex. We presented simultaneous high-pitched and low-pitched tones in an isochronous stream and occasionally presented either the higher or the lower tone 50 ms earlier than expected, while leaving the other tone at the expected time. Here, we investigated the neural basis of carrying rhythmic timing information in lower-pitched voices. Previous work using electroencephalography (EEG) demonstrated that the auditory cortex encodes pitch more robustly in the higher of two simultaneous tones or melodies, and modeling work indicated that this high-voice superiority for pitch originates in the sensory periphery. Interestingly, the main melody (spectral/pitch information) is most often carried by the highest-pitched voice, and the rhythm (temporal foundation) is most often laid down by the lowest-pitched voice. The auditory environment typically contains several sound sources that overlap in time, and the auditory system parses the complex sound wave into streams or voices that represent the various sound sources.
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