The perception of timbral brightness is often predictively described by “sharpness,” which is the conventional predictor described by von Bismarck. The perception of brightness and predicted “sharpness” value increase when the energy of harmonic overtones in high-frequency range increases. Studies regarding the relationship between “sharpness” and harmonic overtones are relatively rare. “Sharpness” and harmonic overtones may have a synergetic effect or a suppression effect over perception of brightness. The electric guitar is one of the representative musical instruments which controls its timbre by adjusting its harmonic overtones. Under the assumption that there is a specific suppression effect, the stimuli generated by a non-linear distortion processor for the electric guitar were compared in the first experiment. The values of “sharpness” were adjusted by shelving filters. The onset of each stimulus was deleted for the second experiment, since any variables other than “sharpness” and the harmonic overtones needed to be eliminated. The result indicated that “sharpness” and the amount of harmonic overtones had a suppression effect. A high amount of harmonic overtones decreased the perception of brightness. This result provokes the question “why did the harmonic overtones suppress the perception of brightness normally predicted by sharpness?” This suppression effect was discussed by observing acoustic features.

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