User:Sonia/Major third
| Inverse | Minor sixth | |
|---|---|---|
| Name | ||
| Other names | - | |
| Abbreviation | M3 | |
| Size | ||
| Semitones | 4 | |
A major third (
Play (help·info)) is one of two commonly occurring musical intervals that span three diatonic scale degrees, the other being the minor third. It is denoted 'major' because it is the larger of the two: the major third is a leap of four semitones, the minor third three. The major third is abbreviated M3; its inversion is the minor sixth. The major third may be derived from the harmonic series as the interval between the fourth and fifth harmonics.
The major scale is so named because of the presence of this interval between its tonic and mediant (1st and 3rd) scale degrees. The major chord also takes its name from the presence of this interval built on the chord's root (provided that the interval of a perfect fifth from the root is also present or implied).
A major third in just intonation most often corresponds to the fifth partial of the overtone series in relation to the fourth, or a pitch ratio of 5:4 (play (help·info)); in equal temperament a major third is equal to four semitones — 400 cents, 13.686 cents wider than the 5:4 major third. The older concept of a ditone (two 9:8 major seconds) made a dissonantly wide major third with the ratio 81:64 (play (help·info)).
In equal temperament three major thirds in a row are equal to an octave (for example, C to E, E to G♯/A♭, and G♯/A♭ to C). This is sometimes called the "circle of thirds". In just intonation, however, three 5:4 major thirds are less than an octave. For example, three 5:4 major thirds from C is B♯ (C to E to G♯ to B♯). The difference between this just-tuned B♯ and an equal temperament C, called a diesis, is about 41 cents.
The major third is classed as an imperfect consonance and is considered one of the most consonant intervals after the unison, octave, perfect fifth, and perfect fourth. In the common practice period, thirds were considered interesting and dynamic consonances along with their inverses the sixths, but in medieval times they were considered dissonances unusable in a stable final sonority.
A diminished fourth is enharmonically equivalent to a major third (that is, it spans the same number of semitones). For example, B–D♯ is a major third; but if the same pitches are spelled B and E♭, the interval is instead a diminished fourth. B–E♭ occurs in the C harmonic minor scale.
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