Perfect fifth
The
perfect fifth or
diapente is a musical interval which is responsible for the most
consonant, or stable, harmony outside of the
unison and
octave. It is a valuable interval in chord structure, song development, and western tuning systems. The prefix
perfect identifies it as belonging to the group of
perfect intervals (
Perfect fourth,
Perfect octave) so called because of their extremely simple pitch relationships resulting in a high degree of
consonance. The perfect fifth is historically relevant because it is the first accepted harmony (besides the octave) of
gregorian chant, a very early formal music composition. The perfect fifth occurs on the
root of all
major and
minor chords (triads) and their
extensions. It is one of three
musical intervals that span five
diatonic scale degrees; the others being the
diminished fifth, which is one
chromatic semitone smaller, and the
augmented fifth, which is one chromatic semitone larger. The
Solfege of the perfect fifth is "Do - So". A helpful way to recognize a perfect fifth is to hum the starting of
twinkle twinkle little star, which is a familiar perfect 5th. The perfect fifth is abbreviated as P5 and its inversion is the
perfect fourth.
Due to its high level of consonance, 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.
A
bare fifth,
open fifth or
empty 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 empty fifth, though these "chords" are common in Christian
Sacred Harp singing and throughout
rock music, especially
hard rock,
metal, and
punk music, where overdriven or distorted guitar can make thirds sound muddy, and fast chord-based passages are made easier to play by combining the four most common guitar hand shapes into one. Rock musicians refer to them as
power chords and often include octave doubling (i.e. their bass note is doubled one octave higher, e.g. F3-C4-F4).
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
semitones, a ratio of 1:2
7/12 (approximately 1.4983), or 700 cents, about two
cents smaller.
The just perfect fifth, together with the
octave, forms the basis of
Pythagorean tuning. A flattened perfect fifth is likewise the basis for
meantone 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 strings on violins, violas, and cellos are all tuned to perfect fifths unless in
scordatura.
*
musical tuning*
diminished fifth*
dominant â€" a perfect fifth above the
tonic*
Tonalsoft Encyclopaedia of Tuning
