Major seventh

In music from Western culture, a seventh is a musical interval encompassing seven staff positions (see Interval number for more details), and the major seventh is one of two commonly occurring sevenths. It is qualified as major because it is the larger of the two. The major seventh spans eleven semitones, its smaller counterpart being the minor seventh, spanning ten semitones. For example, the interval from C to B is a major seventh, as the note B lies eleven semitones above C, and there are seven staff positions from C to B.

Diminished and augmented sevenths span the same number of staff positions, but consist of a different number of semitones (nine and twelve).

The intervals from the tonic (keynote) in an upward direction to the second, to the third, to the sixth, and to the seventh scale degrees (of a major scale) are called major.

A major seventh in just intonation most often corresponds to a pitch ratio of 15:8 (play^ⓘ); in 12-tone equal temperament, a major seventh is equal to eleven semitones, or 1100 cents, about 12 cents wider than the 15:8 major seventh. In 24-tone equal temperament a supermajor seventh, semiaugmented seventh or, semidiminished octave, 23 quarter-tones, is 1150 cents (Play^ⓘ). The small major seventh is a ratio of 9:5, now identified as a just minor seventh. 35:18, or 1151.23 cents, is the ratio of the septimal semi-diminished octave. The 15:8 just major seventh occurs arises in the extended C major scale between C & B and F & E. Play F & E^ⓘ

Under equal temperament, this interval is enharmonically equivalent to a diminished octave (which has a similar musical use to the augmented unison).