What is a Diminished Seventh Chord?

A diminished seventh chord is a four-note chord built by stacking three minor third intervals on top of each other. It contains a root, a minor third, a diminished fifth, and a diminished seventh. For example, a C diminished seventh chord (Cdim7) consists of the notes C, E♭, G♭, and A.

The sound of a diminished seventh chord is very tense and unstable because of the closely spaced intervals. This tension gives the chord a dramatic and mysterious quality that is often used to create suspense in music. Because all the intervals are symmetrical, the chord can easily shift between different tonal centers.

Diminished seventh chords are commonly used in classical music, jazz, and film scores to create strong harmonic tension before resolving to another chord. They often function as passing chords or leading chords that guide the listener toward a more stable harmony. Because of their intense and distinctive sound, diminished seventh chords are an important tool for composers and musicians.