Disco lives: Crank up the bass? Here's why

Proc Natl Acad Sci U S A. 2014 Jun 30. pii: 201402039. [Epub ahead of print]

Superior time perception for lower musical pitch explains why bass-ranged instruments lay down musical rhythms.

Hove MJ1, Marie C2, Bruce IC3, Trainor LJ4.

Author information

• 1Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada L8S 4K1;Martinos Center for Biomedical Imaging, Harvard Medical School/Massachusetts General Hospital, Boston, MA 02129;
• 2Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada L8S 4K1;McMaster Institute for Music and the Mind, Hamilton, ON, Canada L8S 4K1;
• 3McMaster Institute for Music and the Mind, Hamilton, ON, Canada L8S 4K1;Department of Electrical and Computer Engineering, McMaster University, Hamilton, ON, Canada L8S 4K1; and.
• 4Department of Psychology, Neuroscience and Behaviour, McMaster University, Hamilton, ON, Canada L8S 4K1;McMaster Institute for Music and the Mind, Hamilton, ON, Canada L8S 4K1;Rotman Research Institute, Baycrest Hospital, Toronto, ON, Canada M6A 2E1 ljt@mcmaster.ca.

Abstract

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. Music is also often polyphonic. 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. 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. Here, we investigated the neural basis of carrying rhythmic timing information in lower-pitched voices. 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. 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. A behavioral motor task revealed that tapping synchronization was more influenced by the lower-pitched stream. Results from a biologically plausible model of the auditory periphery suggest that nonlinear cochlear dynamics contribute to the observed effect. 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.