# A♭ Diminished piano chord (A♭dim)

A♭dim contains A♭, C♭ and E♭♭. Two stacked minor thirds. A♭ is a black key; C♭ and E♭♭ are white.

- Canonical page: https://piano.org/chords/diminished/a-flat/
- Entity: chord:diminished:a-flat
- Notes: A♭ C♭ E♭♭
- Formula: 1 ♭3 ♭5
- Intervals from root: P1, m3, TT
- Interval stack (semitones): 3 3
- Also written: A♭dim, Abdim, A♭ diminished
- Parameters: A440, 12-TET, 165 mm octave, spans centre to centre

## Construction

| Degree | Note | Interval from root | Semitones |
| --- | --- | --- | --- |
| 1 | A♭ | Perfect unison | 0 |
| ♭3 | C♭ | Minor third | 3 |
| ♭5 | E♭♭ | Tritone | 6 |

## Fingering

Rest your right hand over the notes with finger 1 on A♭, finger 3 on C♭, finger 5 on E♭♭. The left hand mirrors it.
Right hand 1-3-5, left hand 5-3-1. Source: piano.org fingering method v1.

## Inversions

| Position | Bass | Notes in order | Figured bass | Span |
| --- | --- | --- | --- | --- |
| Root position | A♭ | A♭3 C♭3 E♭♭4 | 5/3 | 6 st, 83 mm |
| First inversion (A♭dim/C♭) | C♭ | C♭3 E♭♭4 A♭4 | 6/3 | 9 st, 124 mm |
| Second inversion (A♭dim/E♭♭) | E♭♭ | E♭♭4 A♭4 C♭4 | 6/4 | 9 st, 124 mm |

## Voicings (5)

| Voicing | Notes | Span | Relation | Omits or adds |
| --- | --- | --- | --- | --- |
| Close, root position | A♭3 C♭3 E♭♭4 | 6 st, 83 mm | identical | none |
| Close, first inversion | C♭3 E♭♭4 A♭4 | 9 st, 124 mm | identical | none |
| Close, second inversion | E♭♭4 A♭4 C♭4 | 9 st, 124 mm | identical | none |
| Open, fifth on top | A♭2 E♭♭3 C♭3 | 15 st, 206 mm | identical | none |
| Root and third only | A♭3 C♭3 | 3 st, 41 mm | subset | omits E♭♭ |

## Diatonic function by key

| Key | Roman numeral | Function |
| --- | --- | --- |
| F♯ minor | ii° | Predominant |
| A major | vii° | Dominant function |

Classification system: common-practice functional harmony.

## Progressions (2)

| Progression | Key | Role | Sequence | Voice leading |
| --- | --- | --- | --- | --- |
| ii°, v, i | F♯ minor | ii° | G♯dim to C♯m to F♯m | A♭dim opens the phrase |
| vii°, I | A major | vii° | G♯dim to A | A♭dim opens the phrase |

## One-edit neighbors

| Becomes | Edit | Changes | Common tones |
| --- | --- | --- | --- |
| A♭m7♭5 | 1 ♭3 ♭5 ♭7 | adds G♭ | 3 |
| A♭dim7 | 1 ♭3 ♭5 ♭♭7 | adds G♭♭ | 3 |
| A♭m | 1 ♭3 5 | E♭♭ becomes E♭ | 2 |
| A♭m7 | 1 ♭3 5 ♭7 | E♭♭ becomes E♭, G♭ | 2 |
| A♭mMaj7 | 1 ♭3 5 7 | E♭♭ becomes E♭, G | 2 |
| A♭m6 | 1 ♭3 5 6 | E♭♭ becomes E♭, F | 2 |
| A♭ | 1 3 5 | C♭, E♭♭ becomes C, E♭ | 1 |
| A♭aug | 1 3 ♯5 | C♭, E♭♭ becomes C, E | 1 |
| A♭sus2 | 1 2 5 | C♭, E♭♭ becomes B♭, E♭ | 1 |
| A♭sus4 | 1 4 5 | C♭, E♭♭ becomes D♭, E♭ | 1 |

## Set theory

- Absolute pitch classes: {8, 11, 2}
- Relative pitch classes: [0, 3, 6]
- Normal order: [8, 11, 2]
- Prime form: (036)
- Forte number: 3-10
- Interval vector: <002001>

## Frequencies (close root position)

| Note | MIDI | Frequency |
| --- | --- | --- |
| A♭3 | 56 | 207.65 Hz |
| C♭3 | 59 | 246.94 Hz |
| E♭♭4 | 62 | 293.66 Hz |

## Questions and answers

### What notes are in A♭dim?

A♭dim contains A♭, C♭ and E♭♭. The formula is 1, ♭3, ♭5.

### How do you play A♭dim on piano?

Play A♭, C♭ and E♭♭ together. Right hand fingers 1, 3, 5; left hand 5, 3, 1. A♭ is a black key; C♭ and E♭♭ are white.

### What are the inversions of A♭dim?

3 positions: root position A♭ C♭ E♭♭, A♭dim/C♭, A♭dim/E♭♭.

### What keys contain A♭dim?

2: ii° in F♯ minor, vii° in A major.

### What is the difference between A♭dim and A♭m7♭5?

Adds G♭. 3 of the notes are shared.

### What is an easy A♭dim for small hands?

The root and third only voicing, A♭3 C♭3, spans 3 semitones or about 41 mm.

### What are the frequencies of A♭dim?

From A♭3 at A440 in 12-TET: 207.65, 246.94, 293.66 Hz.

### What is the set class of A♭dim?

Prime form (036), Forte 3-10, interval vector &lt;002001&gt;.

### How do I transpose A♭dim to another key?

Keep the 1, ♭3, ♭5 formula on the new root. Cdim is C, E♭, G♭; C♯dim is C♯, E, G.

### Is G♯dim the same as A♭dim?

Enharmonically yes: the same piano keys and the same sound, spelled differently.

## Provenance

Every derived value above is computed by the piano.org theory kernel from the root, the quality and the stated parameters. Nothing is hand-entered per chord.

Machine record: https://piano.org/api/knowledge/v1/entities/chord:diminished:a-flat
Last reviewed: 2026-08-12