Perfect fifth
From Freepedia
The perfect fifth or diapente is one of three musical intervals that span five diatonic scale degrees; the others being the diminished fifth, which is one semitone smaller, and the augmented fifth, which is one semitone larger. The prefix perfect identifies it as belonging to the group of perfect intervals, so called because of their extremely simple pitch relationships resulting in a high degree of consonance.
It occurs most commonly built on the root of all major and minor triads and their extensions. However, due to its high level of consonance in this position, the perfect fifth contributes very little to the overall harmonic effect of any chords containing it (power chords excepted). In any situation that necessitates the omission of notes from a chord, such as for practical reasons of fingering, for example, the note forming the perfect fifth above the chord's root can often be safely omitted, its absence being barely, if at all, noticeable.
The 'perfect fifth is abbreviated as P5 and its inversion is the perfect fourth.
A perfect fifth in just intonation, a just fifth, corresponds to a pitch ratio of 3:2, while in 12-tone equal temperament, a perfect fifth is equal to seven (7) semitones, a ratio of 1:27/12 (approximately 1.4983), or 700 cents, about two cents smaller.
The just perfect fifth, together with the octave, forms the basis of Pythagorean tuning.
The circle of fifths is a model of pitch space for the chromatic scale (chromatic circle) which considers nearness not as adjacency but as the number of perfect fifths required to get from one note to another.
The perfect fifth is considered the most consonant interval outside of the unison and octave.
The strings on violins, violas, and cellos are all tuned to perfect fifths unless in scordatura.
A power chord, bare fifth or open fifth is a chord containing only a perfect fifth with no third. The closing chord of Mozart's Requiem is an example of a piece ending on an open fifth, though these "chords" are common in rock music including hard rock, metal, and punk music.
See also
| Perfect fifth | ||||||||
|---|---|---|---|---|---|---|---|---|
| # semitones | Interval class | # cents in equal temperament | Most common diatonic name | Comparable just interval | # cents in just interval | Just interval vs. equal-tempered interval | ||
| 7 | 5 | 700 | perfect fifth | 3:2 | 702 | 2 cents larger | ||
| ||||||||
