# C♯ Augmented 7th piano chord (C♯aug7)

C♯aug7 contains C♯, E♯, G× and B. An augmented triad with the minor seventh added on top. C♯ is a black key; E♯, G× and B are white.

- Canonical page: https://piano.org/chords/augmented-7th/c-sharp/
- Entity: chord:augmented-7th:c-sharp
- Notes: C♯ E♯ G× B
- Formula: 1 3 ♯5 ♭7
- Intervals from root: P1, M3, m6, m7
- Interval stack (semitones): 4 4 2
- Also written: C♯aug7, C#aug7, C♯ augmented 7th
- Parameters: A440, 12-TET, 165 mm octave, spans centre to centre

## Construction

| Degree | Note | Interval from root | Semitones |
| --- | --- | --- | --- |
| 1 | C♯ | Perfect unison | 0 |
| 3 | E♯ | Major third | 4 |
| ♯5 | G× | Minor sixth | 8 |
| ♭7 | B | Minor seventh | 10 |

## Fingering

Rest your right hand over the notes with finger 2 on C♯, finger 3 on E♯, finger 4 on G×, finger 5 on B. 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 | C♯ | C♯3 E♯3 G×3 B3 | 7 | 10 st, 138 mm |
| First inversion (C♯aug7/E♯) | E♯ | E♯3 G×3 B3 C♯4 | 6/5 | 8 st, 110 mm |
| Second inversion (C♯aug7/G×) | G× | G×3 B3 C♯4 E♯4 | 4/3 | 8 st, 110 mm |
| Third inversion (C♯aug7/B) | B | B3 C♯4 E♯4 G×4 | 4/2 | 10 st, 138 mm |

## Voicings (10)

| Voicing | Notes | Span | Relation | Omits or adds |
| --- | --- | --- | --- | --- |
| Close, root position | C♯3 E♯3 G×3 B3 | 10 st, 138 mm | identical | none |
| Close, first inversion | E♯3 G×3 B3 C♯4 | 8 st, 110 mm | identical | none |
| Close, second inversion | G×3 B3 C♯4 E♯4 | 8 st, 110 mm | identical | none |
| Close, third inversion | B3 C♯4 E♯4 G×4 | 10 st, 138 mm | identical | none |
| Drop 2 | G×2 C♯3 E♯3 B3 | 14 st, 193 mm | identical | none |
| Drop 3 | E♯2 C♯3 G×3 B3 | 18 st, 248 mm | identical | none |
| Drop 2 and 4 | C♯2 G×2 E♯3 B3 | 22 st, 303 mm | identical | none |
| Shell, root ♭7 3 | C♯2 B2 E♯3 | 16 st, 220 mm | subset | omits G× |
| Guide tones, 3 and ♭7 | E♯3 B3 | 6 st, 83 mm | subset | omits C♯ and G× |
| Rootless close | E♯3 G×3 B3 | 6 st, 83 mm | subset | omits C♯ |

## One-edit neighbors

| Becomes | Edit | Changes | Common tones |
| --- | --- | --- | --- |
| C♯aug | 1 3 ♯5 | drops B | 3 |
| C♯7 | 1 3 5 ♭7 | G× becomes G♯ | 3 |
| C♯9 | 1 3 5 ♭7 9 | G× becomes G♯, D♯ | 3 |
| C♯ | 1 3 5 | G×, B becomes G♯ | 2 |
| C♯maj7 | 1 3 5 7 | G×, B becomes G♯, B♯ | 2 |
| C♯m7 | 1 ♭3 5 ♭7 | E♯, G× becomes E, G♯ | 2 |
| C♯m7♭5 | 1 ♭3 ♭5 ♭7 | E♯, G× becomes E, G | 2 |
| C♯7sus4 | 1 4 5 ♭7 | E♯, G× becomes F♯, G♯ | 2 |
| C♯6 | 1 3 5 6 | G×, B becomes G♯, A♯ | 2 |
| C♯add9 | 1 3 5 9 | G×, B becomes G♯, D♯ | 2 |

## Set theory

- Absolute pitch classes: {1, 5, 9, 11}
- Relative pitch classes: [0, 4, 8, 10]
- Normal order: [9, 11, 1, 5]
- Prime form: (0248)
- Forte number: 4-24
- Interval vector: <020301>

## Frequencies (close root position)

| Note | MIDI | Frequency |
| --- | --- | --- |
| C♯3 | 49 | 138.59 Hz |
| E♯3 | 53 | 174.61 Hz |
| G×3 | 57 | 220.00 Hz |
| B3 | 59 | 246.94 Hz |

## Questions and answers

### What notes are in C♯aug7?

C♯aug7 contains C♯, E♯, G× and B. The formula is 1, 3, ♯5, ♭7.

### How do you play C♯aug7 on piano?

Play C♯, E♯, G× and B together. Right hand fingers 2, 3, 4, 5; left hand 5, 4, 3, 2. C♯ is a black key; E♯, G× and B are white.

### What are the inversions of C♯aug7?

4 positions: root position C♯ E♯ G× B, C♯aug7/E♯, C♯aug7/G×, C♯aug7/B.

### What is the difference between C♯aug7 and C♯aug?

Drops B. 3 of the notes are shared.

### What is an easy C♯aug7 for small hands?

The guide tones, 3 and ♭7 voicing, E♯3 B3, spans 6 semitones or about 83 mm.

### What are the frequencies of C♯aug7?

From C♯3 at A440 in 12-TET: 138.59, 174.61, 220.00, 246.94 Hz.

### What is the set class of C♯aug7?

Prime form (0248), Forte 4-24, interval vector &lt;020301&gt;.

### How do I transpose C♯aug7 to another key?

Keep the 1, 3, ♯5, ♭7 formula on the new root. Caug7 is C, E, G♯, B♭; D♭aug7 is D♭, F, A, C♭.

### Is D♭aug7 the same as C♯aug7?

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:augmented-7th:c-sharp
Last reviewed: 2026-08-12