A diminished seventh chord consists of a root, a minor third, a diminished fifth, and a diminished seventh.

There are three diminished seventh chords in a major scale: the diminished seventh chord built on the second scale degree, the diminished seventh chord built on the fifth scale degree, and the diminished seventh chord built on the seventh scale degree.

A diminished seventh chord is enharmonically equivalent to a half-diminished seventh chord. This means that they have the same notes, but they are spelled differently.

Diminished seventh chords can be used to create tension, resolve to a tonic chord, and add color to a chord progression.

E7 is a dominant seventh chord, not a diminished seventh chord.

The most common way to resolve a diminished seventh chord is to a tonic chord.

The song "All of Me" by John Legend features a diminished seventh chord in the chorus.

The diminished seventh chord built on the root note of the C major scale is Cdim7.

Bdim7 is enharmonically equivalent to a minor seventh chord.

The diminished seventh chord built on the fifth scale degree of the G major scale is Ddim7.

Edim7 is enharmonically equivalent to an augmented sixth chord.

The diminished seventh chord built on the seventh scale degree of the F major scale is Edim7.

Fdim7 is enharmonically equivalent to a half-diminished seventh chord.

The diminished seventh chord built on the second scale degree of the Bb major scale is Ddim7.

Bbdim7 is enharmonically equivalent to a dominant seventh chord.