A diminished chord (Adim)
The A diminished chord (Adim) is a diminished triad: A, C and E♭, two minor thirds stacked on top of each other (root, minor third and diminished fifth).
It is the vii° in B♭ major and the vii° in B♭ minor; it sits inside F dominant seventh and tends to resolve to B♭ major, a half step up.
Below: voicings, notes on the fretboard, ukulele, piano, inversions and progressions.
How to play A diminished on guitar
There are 3 guitar voicings.
Frets from the 6th string to the 1st: x = not played, 0 = open string.
- Voicing 1: x-0-1-2-1-x, open position, with A in the bass (fingers x-0-1-3-2-x).
- Voicing 2: 5-6-7-5-x-x, barre at fret 5, with A in the bass (fingers 1-2-4-1-x-x).
- Voicing 3: x-12-13-14-13-x, with A in the bass (fingers x-1-2-4-3-x).
Notes of the A diminished chord on the fretboard
A diminished has 3 notes: A, C and E♭. This is where they fall on each string, from the nut to the 12th fret (fret number in parentheses):
- String 6 (E): A (5) · C (8) · E♭ (11)
- String 5 (A): A (0) · C (3) · E♭ (6) · A (12)
- String 4 (D): E♭ (1) · A (7) · C (10)
- String 3 (G): A (2) · C (5) · E♭ (8)
- String 2 (B): C (1) · E♭ (4) · A (10)
- String 1 (E): A (5) · C (8) · E♭ (11)
Formula and intervals of A diminished
Its formula is 1-♭3-♭5; in semitones from the root, 0-3-6.
- A: Root, the note that gives the chord its name
- C: Minor third (m3), 3 semitones above A
- E♭: Diminished fifth (d5), 6 semitones above A
A diminished on ukulele
- Ukulele (G C E A): 5-3-5-0; it sounds C, E♭, A and A.
A diminished on piano
- Keys: A4, C5 and E♭5.
Inversions of A diminished
Each inversion puts a different note in the bass.
- Root position: A, C and E♭, with A in the bass.
- First inversion (Adim/C): C, E♭ and A, with C in the bass.
- Second inversion (Adim/E♭): E♭, A and C, with E♭ in the bass.
Keys that use A diminished
A diminished appears in 3 major and minor keys.
| Key | Degree | Function |
|---|---|---|
| B♭ major (2 flats) | vii° | Leading tone |
| G minor (2 flats) | ii° | Supertonic |
| B♭ minor (harmonic minor, 5 flats) | vii° | Leading tone |
Progressions with A diminished
- Passing diminished chord in A♭ major (I–♯i°–ii–V): A♭ – Adim – B♭m – E♭
Frequently asked questions
What notes are in the A diminished chord?
A, C and E♭: root, minor third and diminished fifth. Its formula is 1-♭3-♭5.
Which keys use A diminished?
Mainly as the vii° in B♭ major and the vii° in B♭ minor. In total it appears in 3 major and minor keys.
Is A diminished the same as a diminished seventh chord?
No: A diminished is a triad with three notes (A, C and E♭). A diminished seventh chord adds a fourth note, another minor third on top.
Why does A diminished sound like F dominant seventh?
Because its three notes, A, C and E♭, are the third, fifth and seventh of F dominant seventh: it is that dominant seventh without its root. So it does the same job and resolves to B♭ major.