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In music, a power chord is a bare fifth usually played on electric guitar. Traditionally the term chord is understood to mean three or more distinct notes, however this usage is well-accepted amongst guitar players. Therefore, many non-guitar players would consider a power chord to be a dyad or simply a harmonic interval. However, a power chord is conceived of and intended to be a minor or major triad with the third degree omitted.
Although the use of the term power chord has, to some extent, spilled over into the vocabulary of other instrumentalists, namely keyboard and synthesizer players, it remains essentially a part of rock guitar culture and is most strongly associated with the overdriven electric guitar styles of hard rock, heavy metal, punk rock, and similar genres. While the term "power chord" is used to refer to a harmonic perfect fifth in a literal sense, with or without octave doubling, and its inversion may appear to be a harmonic perfect fourth, this is an incorrect interpretation (see Harmonic Implications below). However, when the same interval is found in traditional and classical music, the harmonic interpretation will be much more varied, not necessarily implying a triad with the third degree omitted.
Power chords are sometimes notated 5, as in C5 (C power chord), in which case it specifically refers to playing the root and fifth of the chord, in this case C and G, possibly inverted, and possibly with octave doublings.
The term "power chord" refers to the sonic effect of a harmonic perfect fifth or perfect fourth interval, often being distorted through an overdriven amplifier or an electronic processor such as a fuzz box. Even normally consonant major and minor chords can sometimes sound dissonant and unstable when a high level of distortion is introduced. When minor or major chords are used with distortion, the relative intensities of each note's overtone series combine by non-linear intermodulation to form unpredictable sum and difference frequencies, which results in dissonance. Therefore, rock guitarists often use the power chord because it allows for much greater levels of distortion without causing the inharmonicity that including the third interval played at similarly high distortion levels would. The minimalistic nature of the chords maximises the distortion range, thereby adding a feel of 'Power' to the chords. Removing the third from triads to eliminate unwanted sonic effects from distortion has harmonic ramifications, as power chords are ambiguous, having no intrinsic quality, although quality is often implied.
According to an article in the Free Lance-Star, the power chord was pioneered by rock and roll guitarist Link Wray (). Blues guitarist Elmore James used power chords with distortion in the late 1950s, in the song "I Need You".