Fig. 1.

Example chords: the perfect fifth (Left; conventionally consonant), and the minor second (Right; conventionally dissonant) composed of saxophone notes. (A) Musical notation. (B) Amplitude spectra. Spectrum of lower (root) note is shown in blue, that of higher note in red. Blue and red dots denote the frequencies belonging to each note. In the consonant perfect fifth, the two notes share common frequencies and produce an aggregate spectrum that is harmonic (corresponding to a harmonic series with a lower F0, indicated by the vertical bars at the top). In the dissonant minor second, the notes share no harmonics and the overall spectrum is inharmonic. (C) Predicted activation of auditory nerve fibers (55) for each chord. The beating produced by the closely spaced frequencies of the minor second is visible in the low frequency channels of the right-hand plot.