A Diminished 7th
Hear the A Diminished 7th chord played for you.
A°7
A – C – D♯ – F♯
Formula:R-m3-d5-d7
Intervals:P1-m3-d5-d7
Scale Degrees:1-b3-b5-bb7
Introduction
The A Diminished 7th chord is a four-note chord made up of A, C, D♯, and F♯. It is built from a root, minor third, diminished fifth, and diminished seventh.
The A Diminished 7th piano chord (Adim7) consists of the notes A, C, D#, F#. It is built by stacking three minor thirds, creating a fully symmetrical 4-note chord, giving it a extremely tense and dramatic character, fully symmetrical and harmonically versatile. Formula: R-m3-d5-d7 | Scale degrees: 1-b3-b5-bb7.
Notes
A Diminished 7th Inversions
| Position | Notes |
|---|---|
| Root Position | A – C – D♯ – F♯ |
| 1st Inversion | C – D♯ – F♯ – A |
| 2nd Inversion | D♯ – F♯ – A – C |
| 3rd Inversion | A – C – D♯ – F♯ |
Key Signature
The key of A Diminished 7th has 3 sharps.
F♯C♯G♯
Order of sharps
Sharps are added to a key signature in a fixed order. Each new sharp key adds the next sharp on the list.
F♯C♯G♯D♯A♯E♯B♯
Mnemonic: Father Charles Goes Down And Ends Battle
Chords in the Key of A Major
These are the diatonic triads built on each degree of the A major scale:
C
D
E
F
G
A
B
C
D
E
F
G
A
B
I — A Major (major)
Theory: Intervals
Formula: R-m3-d5-d7
Intervals: P1-m3-d5-d7
The A Diminished 7th is built by stacking intervals from the root note. The formula R-m3-d5-d7 describes the scale degrees used. The intervals P1-m3-d5-d7 show the distance between each note in the chord.
A Diminished 7th — Frequently Asked Questions
What notes are in the A Diminished 7th chord?
The A Diminished 7th chord (Adim7) contains four notes: A (root), C (minor third), Eb (diminished fifth), and Gb (diminished seventh). All four notes are spaced exactly 3 semitones apart, making this a perfectly symmetrical chord.
How does A Diminished 7th differ from A Diminished?
A Diminished is a three-note triad (A, C, Eb). A Diminished 7th adds Gb as the diminished seventh, completing the symmetrical four-note structure and maximising harmonic tension.
Why is the Diminished 7th chord symmetrical?
Adim7 contains the same pitches as Cdim7, Ebdim7, and Gbdim7 — all inversions of the same four notes (C, Eb, Gb, A). Only three unique dim7 chords exist.
How is A Diminished 7th used in music?
Adim7 functions as the vii°7 of Bb, resolving up by half step to Bb Major. It is common in classical music, jazz, and gospel as a leading-tone chord and chromatic passing chord. Bb Major is one of the most important keys in jazz.
What songs use Diminished 7th chords?
Diminished 7th chords appear in Michelle (Beatles), throughout Chopin and Beethoven, and in jazz standards. Adim7 often appears in pieces in Bb Major as the leading-tone chord.
How many unique Diminished 7th chords exist?
Only three. Adim7 shares its notes with Cdim7, Ebdim7, and Gbdim7. The other two groups are Dbdim7 and Ddim7.
Practice Tips
- Play Adim7 (A–C–Eb–Gb) — notice how every note is exactly 3 semitones from the next.
- Adim7 resolves to Bb Major: practice Adim7 → Bb as the leading-tone resolution in one of jazz's most common keys.
- Verify: Adim7 and Cdim7 contain identical notes — play both to confirm the symmetry.
- Use Adim7 as a chromatic passing chord: Am7 → Adim7 → G/B for smooth classical voice leading.
- The notes A–C–Eb–Gb form a pattern of alternating white and black keys — a helpful physical memory anchor.
- Compare Adim7 with Am7 — both start on A, but dim7 creates maximum drama while m7 is smooth and melancholy.
Related Tools
Chord FinderLook up any chord — see the notes, hear it, and play along.Chord DrillTimed drills to build speed and recognition across all chord types.Practice RoomPlug in a MIDI keyboard and get real-time feedback on every chord and scale.Circle of FifthsVisualize key relationships, relative minors, and key signatures.MIDI MonitorLive MIDI message stream with note names, velocity, and a scrolling staff.