Diminished triad chord

A diminished triad chord or diminished chord () is a triad consisting of two minor thirds above the root — if built on C, a diminished chord would have a C, an E♭ and a G♭.^[2] It resembles a minor triad with a lowered (flattened) fifth.

In the common practice period, the diminished chord is considered dissonant, or unstable. It lacks tonal center or drive because the diminished fifth symmetrically divides the octave.

A diminished chord occurs in a major scale only on the seventh scale degree; in the key of C, this is a B diminished chord (B, D, F). This also occurs in the seventh chord built on the fifth note; in C, this is G dominant seventh (G, B, D, F).

In a twelve-tone equal tempered tuning, a diminished chord has 3 semitones between the third and fifth, 3 between the root and third, and 6 between the root and fifth. It is represented by the integer notation {0, 3, 6}. In just intonation, the diminished triad on vii is tuned 135:162:160. According to Sorge the trumpet, in its overtone series on C, gives the diminished triad e-g-b♭ = 5:6:7 ("perfect diminished chord"^[3]), but the 7 is too flat and 45:54:64 is preferred.^[1] Helmholtz describes the diminished triad as b₁−d | f, giving a just minor third and Pythagorean minor third in the notation system used in On the Sensations of Tone as a Physiological Basis for the Theory of Music.^[4]

In most sheet music books , Cdim or C° denotes a diminished seventh chord (a four note chord) with root C, and Cm-5 or Cm♭5 denotes a diminished triad with root C. However, in some modern jazz books and some music theory literature , Cdim or C° denotes a diminished triad, while Cdim7 or C°7 denotes a diminished seventh chord.

"In [rock and] pop music, the diminished triad nearly always appears on the second scale degree, forming a generally maudlin and dejected ii^o with its members, 2—4—♭6."^[5] Songs that feature ii^o include Santo & Johnny's Sleep Walk, Herb Alpert's "This Guy's in Love with You", Jay and the Americans' "Cara Mia", and The Hollies' "The Air That I Breathe".^[5] Not so rare but rare enough so as to imply knowledge of and conscious avoidance on the part of rock musicians, examples of its use include Oasis' "Don't Look Back In Anger", David Bowie's "Space Oddity", and two in Paul Young's "Go Away".^[6]

The ii^o6 chord is usually found in first inversion, since it is diminished with the bass note doubled since it is not a part of the tritone, while the vii^o7 chord appears with all four factors most often in root position.^[7] In both cases resolve the bass up and move the upper voices downwards in contrary motion.^[7] The popular music symbol for a diminished triad is a capital letter designating the root (as with a major chord) with MI^(♭5) added.^[8] For example BMI^(♭5) (see also Chord names and symbols (jazz and pop music)).

Diminished chord table

See also

• Half-diminished seventh chord
• Secondary leading-tone chord

Sources

1. ^ ^{a b} Shirlaw, Matthew (). The Theory of Harmony, p.304. ISBN 9781451015348.
2. ^ Benward & Saker (2003). Music: In Theory and Practice, Vol. I, p.68. Seventh Edition. ISBN 978-0-07-294262-0.
3. ^ Fétis, François-Joseph and Arlin, Mary I. (1994). Esquisse de l'histoire de l'harmonie, p.139n9. ISBN 9780945193517.
4. ^ Hermann von Helmholtz (1885). On the Sensations of Tone as a Physiological Basis for the Theory of Music, p.344. Longmans, Green.
5. ^ ^{a b} Everett, Walter (2009). The Foundations of Rock, p.195. ISBN 9780195310238.
6. ^ Stephenson, Ken (2002). What to Listen for in Rock: A Stylistic Analysis, p.85. ISBN 9780300092394.
7. ^ ^{a b} Benward & Saker (2009). Music in Theory and Practice: Volume II, p.76. Eighth Edition. ISBN 978-0-07-310188-0.
8. ^ Benward & Saker (2003), p.77.

Degrees and functions of the diatonic scale (♭) Tonic Supertonic Subdominant parallel Mediant Dominant parallel Tonic counter parallel Subdominant Dominant Submediant Tonic parallel Subtonic Leading incomplete dominant seventh C D E F G A B♭ B