Inverse | augmented fifth |
---|---|
Name | |
Other names | - |
Abbreviation | d4[1] |
Size | |
Semitones | 4 |
Interval class | 4 |
Just interval | 32:25,[2] 8192:6561, 14:11 |
Cents | |
12-Tone equal temperament | 400 |
Just intonation | 427, 384, 417.5 |
In classical music from Western culture, a diminished fourth ( ) is an interval produced by narrowing a perfect fourth by a chromatic semitone.[1][3] For example, the interval from C to F is a perfect fourth, five semitones wide, and both the intervals from C♯ to F, and from C to F♭ are diminished fourths, spanning four semitones. Being diminished, it is considered a dissonant interval.[4]
A diminished fourth is enharmonically equivalent to a major third; that is, it spans the same number of semitones, and they are physically the same pitch in twelve-tone equal temperament. For example, B–D♯ is a major third; but if the same pitches are spelled B and E♭, as occurs in the C harmonic minor scale, the interval is instead a diminished fourth. In other tunings, however, they are not necessarily identical. For example, in 31 equal temperament the diminished fourth is slightly wider than a major third, and is instead the same width as the septimal major third. The Pythagorean diminished fourth (F♭--, 8192:6561 = 384.36 cents), also known as the schismatic major third, is closer to the just major third than the Pythagorean major third.
In just intonation the usual diminished fourth: the interval C♯ to F, a diatonic minor second plus a pure minor third, or the interval C to F♭, a minor third plus a diatonic minor second, is 16/15 * 6/5 = 32/25.
The 32:25 just diminished fourth arises in the C harmonic minor scale between B and E♭.[5]