Central auditory processing of noncontextual consonance in music: an evoked potential study.

The consonance of individual chords presented out of musical context, or the noncontextual consonance of chords, is usually defined as the absence of roughness, which is a sensation perceived when slightly mistuned frequencies are not clearly resolved in the cochlea. The present work uses evoked potentials to demonstrate that the absence of roughness is not sufficient to explain the entirety of noncontextual consonance perception. Presented with a random sequence of various pure-tone intervals (0-13 semitones), listeners' cerebral cortical activities distinguished these stimuli according to their noncontextual consonance in a manner consistent with standard musical practice, even when the intervals exceeded the critical bandwidth (approximately three semitones). The roughness-based model of noncontextual consonance could not account for this result because these wide intervals had indistinguishably low levels of roughness. Further, this effect was evident only in musicians, indicating plasticity in the underlying neural mechanisms. The results are consistent with the hypothesis that, although the absence of roughness may represent an important aspect of noncontextual consonance, properties of intervals other than those related to roughness also contribute to this perception, underpinned by neural activity in the central auditory system that can be plastically modified by experience.