# A♯ Diminished piano chord (A♯dim)

A♯dim contains A♯, C♯ and E. Two stacked minor thirds. A♯ and C♯ are black keys; E is white.

- Canonical page: https://piano.org/chords/diminished/a-sharp/
- Entity: chord:diminished:a-sharp
- Notes: A♯ C♯ E
- Formula: 1 ♭3 ♭5
- Intervals from root: P1, m3, TT
- Interval stack (semitones): 3 3
- Also written: A♯dim, A#dim, 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♯4 E4 | 5/3 | 6 st, 83 mm |
| First inversion (A♯dim/C♯) | C♯ | C♯4 E4 A♯4 | 6/3 | 9 st, 124 mm |
| Second inversion (A♯dim/E) | E | E4 A♯4 C♯5 | 6/4 | 9 st, 124 mm |

## Voicings (5)

| Voicing | Notes | Span | Relation | Omits or adds |
| --- | --- | --- | --- | --- |
| Close, root position | A♯3 C♯4 E4 | 6 st, 83 mm | identical | none |
| Close, first inversion | C♯4 E4 A♯4 | 9 st, 124 mm | identical | none |
| Close, second inversion | E4 A♯4 C♯5 | 9 st, 124 mm | identical | none |
| Open, fifth on top | A♯2 E3 C♯4 | 15 st, 206 mm | identical | none |
| Root and third only | A♯3 C♯4 | 3 st, 41 mm | subset | omits E |

## Diatonic function by key

| Key | Roman numeral | Function |
| --- | --- | --- |
| G♯ minor | ii° | Predominant |
| B major | vii° | Dominant function |

Classification system: common-practice functional harmony.

## Progressions (2)

| Progression | Key | Role | Sequence | Voice leading |
| --- | --- | --- | --- | --- |
| ii°, v, i | G♯ minor | ii° | A♯dim to D♯m to G♯m | A♯dim opens the phrase |
| vii°, I | B major | vii° | A♯dim to B | 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: {10, 1, 4}
- Relative pitch classes: [0, 3, 6]
- Normal order: [10, 1, 4]
- Prime form: (036)
- Forte number: 3-10
- Interval vector: <002001>

## Frequencies (close root position)

| Note | MIDI | Frequency |
| --- | --- | --- |
| A♯3 | 58 | 233.08 Hz |
| C♯4 | 61 | 277.18 Hz |
| E4 | 64 | 329.63 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♯ and C♯ are black keys; E is 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 G♯ minor, vii° in B 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♯4, spans 3 semitones or about 41 mm.

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

From A♯3 at A440 in 12-TET: 233.08, 277.18, 329.63 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 B♭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-sharp
Last reviewed: 2026-08-12