R esearch on rock harmony accords with common practice in guitar playing in that power chords (fifth interval) with an indeterminate chord quality as well as major chords are preferred to more complex chords when played with a distorted tone. This study explored the interrelated effects of distortion and harmonic structure on acoustic features and perceived pleasantness of electric guitar chords. Extracting psychoacoustic parameters from guitar tones with Music Information Retrieval technology revealed that the level of distortion and the complexity of interval relations affects sensorial pleasantness. A listening test demonstrated power and major chords being perceived as significantly more pleasant than minor and altered dominant chords when being played with an overdriven or distorted guitar tone. This result accords with musical practice within rock genres. Rather clean rock styles such as blues or classic rock use major chords frequently, whereas subgenres with more distorted guitars such as heavy metal largely prefer power chords. Considering individual differences, electric guitar players rated overdriven and distorted chords as significantly more pleasant. Results were ambiguous in terms of gender but indicated that women perceive distorted guitar tones as less pleasant than men. Rock music listeners were more tolerant of sensorial unpleasant sounds.

Guitar distortion used in rock music modifies a chord so that new frequencies appear in its harmonic structure. A distorted dyad (power chord) has a special role in heavy metal music due to its harmonics that create a major third interval, making it similar to a major chord. We investigated how distortion affects cortical auditory processing of chords in musicians and nonmusicians. Electric guitar chords with or without distortion and with or without the interval of the major third (i.e., triads or dyads) were presented in an oddball design where one of them served as a repeating standard stimulus and others served as occasional deviants. This enabled the recording of event-related potentials (ERPs) of the electroencephalogram (EEG) related to deviance processing (the mismatch negativity MMN and the attention-related P3a component) in an ignore condition. MMN and P3a responses were elicited in most paradigms. Distorted chords in a nondistorted context only elicited early P3a responses. However, the power chord did not demonstrate a special role in the level of the ERPs. Earlier and larger MMN and P3a responses were elicited when distortion was modified compared to when only harmony (triad vs. dyad) was modified between standards and deviants. The MMN responses were largest when distortion and harmony deviated simultaneously. Musicians demonstrated larger P3a responses than nonmusicians. The results suggest mostly independent cortical auditory processing of distortion and harmony in Western individuals, and facilitated chord change processing in musicians compared to nonmusicians. While distortion has been used in heavy rock music for decades, this study is among the first ones to shed light on its cortical basis.