power chord
A chord consisting of only the root and fifth (and often the octave), without a third, producing a neutral, heavy sound used extensively in rock and metal.
In Depth
The power chord (notated as "5" chords, e.g., C5, G5) strips harmony down to its most fundamental interval: the perfect fifth. By omitting the third — the note that determines whether a chord is major or minor — the power chord is neither major nor minor, creating an ambiguous, raw, and powerful sound. When played through a distorted electric guitar amplifier, the overtones generated by the distortion fill in harmonic content, giving power chords a massive, complex sound from just two notes.
Power chords became the foundation of hard rock and punk in the 1960s and 70s — Pete Townshend, the Ramones, and Black Sabbath built entire songs from power chord progressions. The technique works because guitar distortion generates intermodulation products (sum and difference tones) from the notes played; a perfect fifth produces harmonious overtones, while a major or minor third through heavy distortion creates dissonant beating. This acoustic fact explains why power chords sound clean through distortion while full chords sound muddy — physics, not just aesthetics, dictates the technique.
The reason power chords work through distortion but full chords sound muddy is pure physics: the perfect fifth (3:2 ratio) generates harmonious overtones through distortion, while thirds create dissonant intermodulation products.