Diminished triad chord

A diminished triad chord ( Play (help·info)) is a triad consisting of a minor third and a diminished fifth above the root — if built on C, a diminished chord would have a C, an E♭ and a G♭. 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 most sheet music books, Cdim or C° denotes a diminished seventh chord (a four note chord) with root C, and Cm-5 or Cmb5 denotes a diminished triad with root C. Howevever, 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.

See also

• half-diminished seventh chord.