Adim chord on piano
The Adim chord, or A diminished, stacks 3 notes on A: A, C and E♭. Musicians write its formula 1 ♭3 ♭5.
Notes and intervals of Adim
Each note of Adim has a job. Counted from the root, you get root (A), minor 3rd (C) and diminished 5th (E♭). Change one of these intervals and you get a different chord, which is why the formula 1 ♭3 ♭5 is worth memorising rather than the shape alone.
| Degree | Interval | Note |
|---|---|---|
| 1 | root | A |
| ♭3 | minor 3rd | C |
| ♭5 | diminished 5th | E♭ |
How to play Adim on piano
Put your right-hand thumb on A, then add the other notes: A, C and E♭. Teachers usually suggest the fingering 1-3-5 (left hand: 5-3-1). Press the keys together, release, and repeat until the chord sounds even.
Inversions of Adim
An inversion keeps the same notes but puts another one in the bass. Adim has 2 inversions besides root position: 1st inversion (C E♭ A) and 2nd inversion (E♭ A C). Inversions let you move between chords with tiny hand movements, which is how pianists make progressions sound smooth.
Which keys use Adim?
You find Adim as a diatonic chord in B flat major (vii°). The most common case is B flat major, where it plays the role of vii°.
Scales to play over Adim
These scales share every note of Adim: A blues scale and A Locrian mode. A blues scale is the safest choice; the others add more colour.
About diminished chords
Two stacked minor thirds: 1 ♭3 ♭5. The diminished fifth (a tritone) makes the diminished chord the most unstable triad: tense, dark and restless. It rarely stands alone and pulls towards the chord a semitone above its root. For example Bdim: B D F. Add a diminished seventh and you get the symmetrical diminished seventh chord.
In a major key it sits on vii° (for example Bdim in C major), acting as a lighter V7 that resolves to I. In a minor key it sits on ii°. Passing diminished chords connect neighbouring chords chromatically, for example I ♯i° ii (C C♯dim Dm). Classical music, jazz, ragtime and film scores use it to build suspense.
Root position 1 ♭3 ♭5 sits under fingers 1 3 5. Because it is so unstable, voice-lead it: keep each note within a semitone or a tone of where the next chord's notes are. In classical harmony vii° is often played in first inversion (third in the bass), with that bass note doubled rather than the root.
dim (three notes) and dim7 (four notes, with a diminished seventh) are not the same, though 'dim' on a jazz chart often means dim7. And dim is not m7♭5: the half-diminished chord adds a minor seventh (for example Bm7♭5: B D F A) and sounds much softer. Symbols: ° means diminished, ø means half-diminished.
Frequently asked questions
What notes are in the Adim chord?
Adim (A diminished) contains A, C and E♭. In intervals: root (A), minor 3rd (C) and diminished 5th (E♭).
How do you play Adim on piano?
Play A, C and E♭ together with the right-hand fingering 1-3-5. You can also play it in 2 inversions, shown on this page.
What scale goes with Adim?
A blues scale fits Adim best. Other scales that contain all its notes: A Locrian mode.
What key is Adim in?
Adim belongs to B flat major (vii°). In B flat major it is the vii° chord.
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