# A♯ Half Diminished 7th piano chord (A♯m7♭5)

A♯m7♭5 contains A♯, C♯, E and G♯. A diminished triad with the minor seventh added on top. A♯, C♯ and G♯ are black keys; E is white.

- Canonical page: https://piano.org/chords/half-diminished/a-sharp/
- Entity: chord:half-diminished-7th:a-sharp
- Notes: A♯ C♯ E G♯
- Formula: 1 ♭3 ♭5 ♭7
- Intervals from root: P1, m3, TT, m7
- Interval stack (semitones): 3 3 4
- Also written: A♯m7♭5, A#m7b5, A♯ half diminished 7th
- 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 |
| ♭7 | G♯ | Minor seventh | 10 |

## Fingering

Rest your right hand over the notes with finger 2 on A♯, finger 3 on C♯, finger 4 on E, finger 5 on G♯. The left hand mirrors it.
Right hand 2-3-4-5, left hand 5-4-3-2. Source: piano.org fingering method v1.

## Inversions

| Position | Bass | Notes in order | Figured bass | Span |
| --- | --- | --- | --- | --- |
| Root position | A♯ | A♯3 C♯4 E4 G♯4 | 7 | 10 st, 138 mm |
| First inversion (A♯m7♭5/C♯) | C♯ | C♯4 E4 G♯4 A♯4 | 6/5 | 9 st, 124 mm |
| Second inversion (A♯m7♭5/E) | E | E4 G♯4 A♯4 C♯5 | 4/3 | 9 st, 124 mm |
| Third inversion (A♯m7♭5/G♯) | G♯ | G♯4 A♯4 C♯5 E5 | 4/2 | 8 st, 110 mm |

## Voicings (10)

| Voicing | Notes | Span | Relation | Omits or adds |
| --- | --- | --- | --- | --- |
| Close, root position | A♯3 C♯4 E4 G♯4 | 10 st, 138 mm | identical | none |
| Close, first inversion | C♯4 E4 G♯4 A♯4 | 9 st, 124 mm | identical | none |
| Close, second inversion | E4 G♯4 A♯4 C♯5 | 9 st, 124 mm | identical | none |
| Close, third inversion | G♯4 A♯4 C♯5 E5 | 8 st, 110 mm | identical | none |
| Drop 2 | E3 A♯3 C♯4 G♯4 | 16 st, 220 mm | identical | none |
| Drop 3 | C♯3 A♯3 E4 G♯4 | 19 st, 261 mm | identical | none |
| Drop 2 and 4 | A♯2 E3 C♯4 G♯4 | 22 st, 303 mm | identical | none |
| Shell, root ♭7 ♭3 | A♯2 G♯3 C♯4 | 15 st, 206 mm | subset | omits E |
| Guide tones, ♭3 and ♭7 | C♯4 G♯4 | 7 st, 96 mm | subset | omits A♯ and E |
| Rootless close | C♯4 E4 G♯4 | 7 st, 96 mm | subset | omits A♯ |

## Diatonic function by key

| Key | Roman numeral | Function |
| --- | --- | --- |
| G♯ minor | iim7♭5 | Predominant |
| B major | viim7♭5 | Dominant function |

Classification system: common-practice functional harmony.

## Progressions (2)

| Progression | Key | Role | Sequence | Voice leading |
| --- | --- | --- | --- | --- |
| ii, v, i | G♯ minor | iim7♭5 | A♯m7♭5 to D♯m7 to G♯m7 | A♯m7♭5 opens the phrase |
| vii, I | B major | viim7♭5 | A♯m7♭5 to Bmaj7 | A♯m7♭5 opens the phrase |

## One-edit neighbors

| Becomes | Edit | Changes | Common tones |
| --- | --- | --- | --- |
| A♯dim | 1 ♭3 ♭5 | drops G♯ | 3 |
| A♯m7 | 1 ♭3 5 ♭7 | E becomes E♯ | 3 |
| A♯dim7 | 1 ♭3 ♭5 ♭♭7 | G♯ becomes G | 3 |
| A♯m9 | 1 ♭3 5 ♭7 9 | E becomes E♯, B♯ | 3 |
| A♯m | 1 ♭3 5 | E, G♯ becomes E♯ | 2 |
| A♯7 | 1 3 5 ♭7 | C♯, E becomes C×, E♯ | 2 |
| A♯mMaj7 | 1 ♭3 5 7 | E, G♯ becomes E♯, G× | 2 |
| A♯aug7 | 1 3 ♯5 ♭7 | C♯, E becomes C×, E× | 2 |
| A♯7sus4 | 1 4 5 ♭7 | C♯, E becomes D♯, E♯ | 2 |
| A♯m6 | 1 ♭3 5 6 | E, G♯ becomes E♯, F× | 2 |

## Set theory

- Absolute pitch classes: {10, 1, 4, 8}
- Relative pitch classes: [0, 3, 6, 10]
- Normal order: [8, 10, 1, 4]
- Prime form: (0258)
- Forte number: 4-27
- Interval vector: <012111>

## Frequencies (close root position)

| Note | MIDI | Frequency |
| --- | --- | --- |
| A♯3 | 58 | 233.08 Hz |
| C♯4 | 61 | 277.18 Hz |
| E4 | 64 | 329.63 Hz |
| G♯4 | 68 | 415.30 Hz |

## Questions and answers

### What notes are in A♯m7♭5?

A♯m7♭5 contains A♯, C♯, E and G♯. The formula is 1, ♭3, ♭5, ♭7.

### How do you play A♯m7♭5 on piano?

Play A♯, C♯, E and G♯ together. Right hand fingers 2, 3, 4, 5; left hand 5, 4, 3, 2. A♯, C♯ and G♯ are black keys; E is white.

### What are the inversions of A♯m7♭5?

4 positions: root position A♯ C♯ E G♯, A♯m7♭5/C♯, A♯m7♭5/E, A♯m7♭5/G♯.

### What keys contain A♯m7♭5?

2: iim7♭5 in G♯ minor, viim7♭5 in B major.

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

Drops G♯. 3 of the notes are shared.

### What is an easy A♯m7♭5 for small hands?

The guide tones, ♭3 and ♭7 voicing, C♯4 G♯4, spans 7 semitones or about 96 mm.

### What are the frequencies of A♯m7♭5?

From A♯3 at A440 in 12-TET: 233.08, 277.18, 329.63, 415.30 Hz.

### What is the set class of A♯m7♭5?

Prime form (0258), Forte 4-27, interval vector &lt;012111&gt;.

### How do I transpose A♯m7♭5 to another key?

Keep the 1, ♭3, ♭5, ♭7 formula on the new root. Cm7♭5 is C, E♭, G♭, B♭; C♯m7♭5 is C♯, E, G, B.

### Is B♭m7♭5 the same as A♯m7♭5?

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:half-diminished-7th:a-sharp
Last reviewed: 2026-08-12