Adim7: A Diminished 7th Piano Chord

First inversion: either hand, fingers low note to high
Hand	Notes	Fingers
Right	C, E♭, G♭, A	1-2-4-5
Left	C, E♭, G♭, A	5-3-2-1

Scale degree, note, and interval measured from the root.
Degree	Note	Interval from root	Semitones
1	A	Perfect unison	0
♭3	C	Minor third	3
♭5	E♭	Tritone	6
♭♭7	G♭	Major sixth	9

Construction

A Diminished 7th = Root + Minor 3rd + Diminished 5th + Major 6th = A, C, E♭, G♭

Note	Interval	Degree
A	Root	1
C	Minor 3rd	♭3
E♭	Diminished 5th	♭5
G♭	Major 6th	6

Fingering

Note	Key color	Right hand	Left hand
A	white	thumb (1)	little finger (5)
C	white	index finger (2)	middle finger (3)
E♭	black	middle finger (3)	index finger (2)
G♭	black	little finger (5)	thumb (1)

Right hand: thumb (1) on A, index finger (2) on C, middle finger (3) on E♭, little finger (5) on G♭.

Left hand: little finger (5) on A, middle finger (3) on C, index finger (2) on E♭, thumb (1) on G♭.

A Diminished 7th Inversions

Root position
A – C – E♭ – G♭
1st inversion (Adim7/C)
C – E♭ – G♭ – A
2nd inversion (Adim7/E♭)
E♭ – G♭ – A – C
3rd inversion (Adim7/G♭)
G♭ – A – C – E♭

Key Signature

A Diminished 7th chord is built from symmetrical or ambiguous intervals, so it doesn't belong to a single key and has no key signature of its own.

Chords in the Key of A Major

These are the triads built on each degree of A Major:

I — A Major (major)

Degree	Numeral	Chord	Quality
1	I	A Major	Major
2	ii	B Minor	Minor
3	iii	C♯ Minor	Minor
4	IV	D Major	Major
5	V	E Major	Major
6	vi	F♯ Minor	Minor
7	vii°	G♯ Diminished	Diminished

Same Notes, Other Names

The notes A – C – E♭ – G♭ aren’t exclusive to this chord. Depending on which note is the bass and how the chord functions, the same pitches also spell the following:

C Diminished 7th→E♭ Diminished 7th→F♯ Diminished 7th→

A Diminished 7th : Frequently Asked Questions

What is the A Diminished 7th chord on piano?

The A Diminished 7th chord contains the notes A – C – E♭ – G♭. On piano, play these notes together to sound the chord.

What notes are in the A Diminished 7th chord?

The A Diminished 7th chord (Adim7) contains four notes: A (root), C (minor third), Eb (diminished fifth), and Gb (diminished seventh). All four notes are spaced exactly 3 semitones apart, making this a perfectly symmetrical chord.

How does A Diminished 7th differ from A Diminished?

A Diminished is a three-note triad (A, C, Eb). A Diminished 7th adds Gb as the diminished seventh, completing the symmetrical four-note structure and maximising harmonic tension.

Why is the Diminished 7th chord symmetrical?

Adim7 contains the same pitches as Cdim7, Ebdim7, and Gbdim7: all inversions of the same four notes (C, Eb, Gb, A). Only three unique dim7 chords exist.

How is A Diminished 7th used in music?

Adim7 functions as the vii°7 of Bb, resolving up by half step to Bb Major. It is common in classical music, jazz, and gospel as a leading-tone chord and chromatic passing chord. Bb Major is one of the most important keys in jazz.

What songs use Diminished 7th chords?

Diminished 7th chords appear in Michelle (Beatles), throughout Chopin and Beethoven, and in jazz standards. Adim7 often appears in pieces in Bb Major as the leading-tone chord.

How many unique Diminished 7th chords exist?

Only three. Adim7 shares its notes with Cdim7, Ebdim7, and Gbdim7. The other two groups are Dbdim7 and Ddim7.

A Diminished 7th in detail

Exact

Every pitch class is present and nothing outside the chord is added.

Type	Notes	Semitones	Span	Omissions and additions	Set relation
Close, root position	A3 C4 E♭4 G♭4	9	124 mm	none	identical
Close, first inversion	C4 E♭4 G♭4 A4	9	124 mm	none	identical
Close, second inversion	E♭4 G♭4 A4 C5	9	124 mm	none	identical
Close, third inversion	G♭4 A4 C5 E♭5	9	124 mm	none	identical
Drop 2	E♭3 A3 C4 G♭4	15	206 mm	none	identical
Drop 3	C3 A3 E♭4 G♭4	18	248 mm	none	identical
Drop 2 and 4	A2 E♭3 C4 G♭4	21	289 mm	none	identical

Reduced

A subset of the pitch classes: the identity is incomplete rather than altered.

Type	Notes	Semitones	Span	Omissions and additions	Set relation
Shell, root ♭♭7 ♭3	A2 G♭3 C4	15	206 mm	omits E♭	subset
Guide tones, ♭3 and ♭♭7	C4 G♭4	6	83 mm	omits A and E♭	subset
Rootless close	C4 E♭4 G♭4	6	83 mm	omits A	subset

Spans are measured centre to centre at a 165 mm octave (standard keyboard geometry).

Position	Bass note	Notes in order	Figured bass	Semitones	Span
Root position	A	A3, C4, E♭4, G♭4	7	9	124 mm
First inversion: Adim7/C	C	C4, E♭4, G♭4, A4	6/5	9	124 mm
Second inversion: Adim7/E♭	E♭	E♭4, G♭4, A4, C5	4/3	9	124 mm
Third inversion: Adim7/G♭	G♭	G♭4, A4, C5, E♭5	4/2	9	124 mm

One position per chord tone in the bass. Spans are for close position: voiced inversions appear under Voicings.

Change one note

Chords a single note away, and what moving that note does.

Chord	Change	Formula	Common tones
Adim	drops G♭	1 ♭3 ♭5	3
Am7♭5	G♭ becomes G	1 ♭3 ♭5 ♭7	3
Am6	E♭ becomes E	1 ♭3 5 6	3
Am	E♭, G♭ becomes E	1 ♭3 5	2
Am7	E♭, G♭ becomes E, G	1 ♭3 5 ♭7	2
AmMaj7	E♭, G♭ becomes E, G♯	1 ♭3 5 7	2
A6	C, E♭ becomes C♯, E	1 3 5 6	2

Frequencies

Note	MIDI	Frequency
A3	57	220.00 Hz
C4	60	261.63 Hz
E♭4	63	311.13 Hz
G♭4	66	369.99 Hz

Reference pitch A440, 12-TET, close root position.

Set theory: prime form, Forte number, interval vector

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

Pair	Interval	Semitones	Interval class
A to C	Minor third	3	3
A to E♭	Tritone	6	6
A to G♭	Major sixth	9	3
C to E♭	Minor third	3	3
C to G♭	Tritone	6	6
E♭ to G♭	Minor third	3	3

Where these facts come from

Every value on this page is derived from the note formula for a diminished 7th applied to the root A, using standard music theory. Nothing here is hand-entered per chord, so the notes, intervals, inversions and frequencies cannot drift out of agreement with each other. Pitches assume 12-TET at A440.

A Diminished 7th

Fingerings

A Diminished 7th: notes and degrees