User:Sonia/Perfect fourth
From Wikipedia, the free encyclopedia
The perfect fourth ( Play (help·info)) is a musical interval which spans four scale degrees. It consists of the note and the note five semitones above it on the musical scale. For example, the interval between a C and the next F above it is a perfect fourth; similarly the interval between a G and the next C above it, between an F and the B flat above it, and so on. The perfect fourth may be derived from the harmonic series as the interval between the third and fourth harmonics.
Inverse | perfect fifth | |
---|---|---|
Name | ||
Other names | diatessaron | |
Abbreviation | P4 | |
Size | ||
Semitones | 5 |
The term perfect identifies this interval as belonging to the group of perfect intervals, so called because they are neither major nor minor (such as thirds, which are either minor or major) but perfect. "Perfect" distinguishes the perfect fourth from the augmented fourth, which is one chromatic semitone larger.
The perfect fourth is occasionally called the diatessaron.[1] It is abbreviated P4. The perfect fourth's inversion is the perfect fifth.
Its most common occurrence is between the fifth and upper root of all major and minor triads and their extensions.
A perfect fourth in just intonation corresponds to a pitch ratio of 4:3, or about 498 cents (Play (help·info)), while in equal temperament a perfect fourth is equal to five semitones, or 500 cents.
A helpful way to recognize a perfect fourth is to hum the starting of the "Bridal Chorus" from Wagner's Lohengrin ("Treulich gefuehrt", the colloquially-titled "Here Comes the Bride"). Other examples are the first two notes of the Christmas carols "Hark! The Herald Angels Sing" and "Away in a Manger".
The perfect fourth is a perfect interval like the unison, octave, and perfect fifth, and it is a sensory consonance. In common practice harmony, however, it is considered a stylistic dissonance in certain contexts, namely in two-voice textures and whenever it appears above the bass.[2] If the bass note also happens to be the chord's root, the interval's upper note almost always temporarily displaces the third of any chord, and is then called a suspended fourth.
Conventionally, adjacent strings of the double bass and of the bass guitar are a perfect fourth apart when unstopped, as are all pairs but one of adjacent guitar strings under standard guitar tuning. Sets of tom-tom drums are also commonly tuned in perfect fourths.