# C Diminished 7th piano chord (Cdim7)

Cdim7 contains C, E♭, G♭ and B♭♭. Three stacked minor thirds. E♭ and G♭ are black keys; C and B♭♭ are white.

- Canonical page: https://piano.org/chords/diminished-7th/c/
- Entity: chord:diminished-7th:c
- Notes: C E♭ G♭ B♭♭
- Formula: 1 ♭3 ♭5 ♭♭7
- Intervals from root: P1, m3, TT, M6
- Interval stack (semitones): 3 3 3
- Also written: Cdim7, Cdim7, C diminished 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♭ | Minor third | 3 |
| ♭5 | G♭ | Tritone | 6 |
| ♭♭7 | B♭♭ | Major sixth | 9 |

## Fingering

Rest your right hand over the notes with finger 1 on C, finger 2 on E♭, finger 3 on G♭, finger 5 on B♭♭. The left hand mirrors it.
Right hand 1-2-3-5, left hand 5-3-2-1. Source: piano.org fingering method v1.

## Inversions

| Position | Bass | Notes in order | Figured bass | Span |
| --- | --- | --- | --- | --- |
| Root position | C | C3 E♭3 G♭3 B♭♭3 | 7 | 9 st, 124 mm |
| First inversion (Cdim7/E♭) | E♭ | E♭3 G♭3 B♭♭3 C4 | 6/5 | 9 st, 124 mm |
| Second inversion (Cdim7/G♭) | G♭ | G♭3 B♭♭3 C4 E♭4 | 4/3 | 9 st, 124 mm |
| Third inversion (Cdim7/B♭♭) | B♭♭ | B♭♭3 C4 E♭4 G♭4 | 4/2 | 9 st, 124 mm |

## Voicings (10)

| Voicing | Notes | Span | Relation | Omits or adds |
| --- | --- | --- | --- | --- |
| Close, root position | C3 E♭3 G♭3 B♭♭3 | 9 st, 124 mm | identical | none |
| Close, first inversion | E♭3 G♭3 B♭♭3 C4 | 9 st, 124 mm | identical | none |
| Close, second inversion | G♭3 B♭♭3 C4 E♭4 | 9 st, 124 mm | identical | none |
| Close, third inversion | B♭♭3 C4 E♭4 G♭4 | 9 st, 124 mm | identical | none |
| Drop 2 | G♭2 C3 E♭3 B♭♭3 | 15 st, 206 mm | identical | none |
| Drop 3 | E♭2 C3 G♭3 B♭♭3 | 18 st, 248 mm | identical | none |
| Drop 2 and 4 | C2 G♭2 E♭3 B♭♭3 | 21 st, 289 mm | identical | none |
| Shell, root ♭♭7 ♭3 | C2 B♭♭2 E♭3 | 15 st, 206 mm | subset | omits G♭ |
| Guide tones, ♭3 and ♭♭7 | E♭3 B♭♭3 | 6 st, 83 mm | subset | omits C and G♭ |
| Rootless close | E♭3 G♭3 B♭♭3 | 6 st, 83 mm | subset | omits C |

## One-edit neighbors

| Becomes | Edit | Changes | Common tones |
| --- | --- | --- | --- |
| Cdim | 1 ♭3 ♭5 | drops B♭♭ | 3 |
| Cm7♭5 | 1 ♭3 ♭5 ♭7 | B♭♭ becomes B♭ | 3 |
| Cm6 | 1 ♭3 5 6 | G♭ becomes G | 3 |
| Cm | 1 ♭3 5 | G♭, B♭♭ becomes G | 2 |
| Cm7 | 1 ♭3 5 ♭7 | G♭, B♭♭ becomes G, B♭ | 2 |
| CmMaj7 | 1 ♭3 5 7 | G♭, B♭♭ becomes G, B | 2 |
| C6 | 1 3 5 6 | E♭, G♭ becomes E, G | 2 |

## Set theory

- Absolute pitch classes: {0, 3, 6, 9}
- Relative pitch classes: [0, 3, 6, 9]
- Normal order: [0, 3, 6, 9]
- Prime form: (0369)
- Forte number: 4-28
- Interval vector: <004002>

## Frequencies (close root position)

| Note | MIDI | Frequency |
| --- | --- | --- |
| C3 | 48 | 130.81 Hz |
| E♭3 | 51 | 155.56 Hz |
| G♭3 | 54 | 185.00 Hz |
| B♭♭3 | 57 | 220.00 Hz |

## Questions and answers

### What notes are in Cdim7?

Cdim7 contains C, E♭, G♭ and B♭♭. The formula is 1, ♭3, ♭5, ♭♭7.

### How do you play Cdim7 on piano?

Play C, E♭, G♭ and B♭♭ together. Right hand fingers 1, 2, 3, 5; left hand 5, 3, 2, 1. E♭ and G♭ are black keys; C and B♭♭ are white.

### What are the inversions of Cdim7?

4 positions: root position C E♭ G♭ B♭♭, Cdim7/E♭, Cdim7/G♭, Cdim7/B♭♭.

### What is the difference between Cdim7 and Cdim?

Drops B♭♭. 3 of the notes are shared.

### What is an easy Cdim7 for small hands?

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

### What are the frequencies of Cdim7?

From C3 at A440 in 12-TET: 130.81, 155.56, 185.00, 220.00 Hz.

### What is the set class of Cdim7?

Prime form (0369), Forte 4-28, interval vector &lt;004002&gt;.

### How do I transpose Cdim7 to another key?

Keep the 1, ♭3, ♭5, ♭♭7 formula on the new root. C♯dim7 is C♯, E, G, B♭; Ddim7 is D, F, A♭, C♭.

## 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-7th:c
Last reviewed: 2026-08-12