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In music theory, a diminished triad is a triad consisting of two above the root. (2025). 9780072942620, McGraw-Hill. ISBN 9780072942620 It is a Minor chord with a lowered (flattened) fifth. When using chord symbols, it may be indicated by the symbols "dim", "", "m5", or "MI(5)".Benward & Saker (2003), p.77. However, in most popular-music chord books, the symbol "dim" or "" represents a diminished seventh chord (a four-tone chord), which in some modern jazz books and music theory books is represented by the "dim7" or "7" symbols.
For example, the diminished triad built on B, written as B, has pitches B-D-F:
The chord can be represented by the integer notation {0, 3, 6}.
In the common practice period, the diminished triad is considered dissonant because of the Tritone (or tritone).
On the other hand, in natural minor scales, the diminished triad occurs on the second scale degree; in the key of C minor, this is the D diminished triad (D, F, A). This triad is consequently called the supertonic diminished triad. Like the supertonic minor triad found in a major key, the supertonic diminished triad has a predominant function, almost always resolving to a dominant functioning chord.
If the music is in a minor key, diminished triads can also be found on the raised seventh note, vii. This is because the ascending melodic minor scale has a raised sixth and seventh degree. For example, the chord progression vii–i is common.
The leading-tone diminished triad and supertonic diminished triad are usually found in first inversion (vii6 and ii6, respectively) since the spelling of the chord forms a diminished fifth with the bass. This differs from the fully diminished seventh chord, which commonly occurs in root position. (2025). 9780073101880, McGraw-Hill. ISBN 9780073101880 In both cases, the bass resolves up and the upper voices move downwards in contrary motion.
The vii in major keys is relatively less common than the ii, but still does happen. It is almost always used to Tonicization the relative minor, in progressions such as vii–V7/vi–vi, which resembles ii–V7–i in the relative minor.
In 5-limit just intonation, the diminished chord on VII (in C: B–D–F) is 15:8, 9:8, and 4:3, while on II (in C: D–F–A) it is 9:8, 4:3, and 8:5 (135:160:192). According to Georg Andreas Sorge, the trumpet, in its overtone series on C, gives the diminished triad E–G–B = 5:6:7 ("perfect diminished chord"), but the harmonic seventh is too flat and 45:54:64 is preferred. Helmholtz describes the diminished triad as 1 − D | F, giving a just minor third and Pythagorean minor third (45:54:64) in the notation system used in On the Sensations of Tone as a Physiological Basis for the Theory of Music.
Play , (5-limit major), or on C.
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| On B | |||||||||
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| !Chord !Root !Minor third !Diminished fifth |
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