What notes are in a D diminished 7 chord?

D°7 contains four notes: D (root), F (minor third), A♭ (diminished fifth), and C♭ (diminished seventh — same pitch as B).

Why is the seventh C♭ instead of B?

The diminished 7th interval requires the seventh letter from the root. From D, the seventh letter is C; the diminished version of that letter is C♭. Calling the note B would skip the C letter and use B twice in the chord spelling.

Is D°7 the same as B°7?

Enharmonically yes — both contain the same four pitches. D°7 (D-F-A♭-C♭) is a flat-side spelling; B°7 (B-D-F-A♭) is the sharp-or-natural-side spelling.

When does D°7 appear in music?

In E♭ minor cadences (where it's the proper local spelling) and in chromatically-modulating music that pivots through dim7 sonorities. Wagner uses dim7 chords this way constantly.

D diminished 7 chord — notes, intervals, and practice

D°7 — D, F, A♭, C♭ — is the vii°7 of E♭ minor and a chromatic dim7 in flat-side keys. The C♭ (enharmonic to B) is the spelling tell that the chord lives inside a deep flat-side context. Like all dim7s, D°7 is symmetric; rotating bass tones produces F°7, A♭°7, and C♭°7 — all the same pitches.

Intervals

The D diminished 7 chord stacks two thirds on the root. Each interval and its size in semitones:

D→Fminor 3rd3 semitones
F→Abminor 3rd3 semitones
Ab→Cbdiminished 7th9 semitones

On the keyboard

Each note of the D diminished 7 chord highlighted on a piano. Pitch class is what matters — any octave works.

On the guitar

One voicing of the D diminished 7 chord on a six-string guitar fretboard.

Common mistakes

The diminished 7th is C♭, enharmonic to B natural. In flat-key contexts (E♭ minor, G♭ major) the C♭ spelling preserves consistency with the surrounding harmony; in sharp-key writing the same chord would respell as B°7 (B-D-F-A♭, often written B-D-F-G♯). Both are correct in their respective contexts.

In context

D°7 → E♭ minor is the leading-tone cadence in E♭ minor. D°7 also appears as a passing chord between D minor and E♭ minor in chromatically-modulating music. In jazz, D°7 functions as a B♭7♭9 with omitted root.

Drill it

The D diminished 7 chord is one of 48 in the Chord Trainer. Open the full trainer to practice it alongside related chords with timing and best-time tracking.

Open the Chord Trainer →Or try today's Etudle puzzle

Frequently asked

What notes are in a D diminished 7 chord?: D°7 contains four notes: D (root), F (minor third), A♭ (diminished fifth), and C♭ (diminished seventh — same pitch as B).
Why is the seventh C♭ instead of B?: The diminished 7th interval requires the seventh letter from the root. From D, the seventh letter is C; the diminished version of that letter is C♭. Calling the note B would skip the C letter and use B twice in the chord spelling.
Is D°7 the same as B°7?: Enharmonically yes — both contain the same four pitches. D°7 (D-F-A♭-C♭) is a flat-side spelling; B°7 (B-D-F-A♭) is the sharp-or-natural-side spelling.
When does D°7 appear in music?: In E♭ minor cadences (where it's the proper local spelling) and in chromatically-modulating music that pivots through dim7 sonorities. Wagner uses dim7 chords this way constantly.