A♯dim7: A♯/B♭ Diminished 7th Piano Chord

Root position: either hand, fingers low note to high
Hand	Notes	Fingers
Right	A♯, C♯, E, G	2-3-4-5
Left	A♯, C♯, E, G	5-4-3-2

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♯	black	index finger (2)	little finger (5)
C♯	black	middle finger (3)	ring finger (4)
E	white	ring finger (4)	middle finger (3)
G	white	little finger (5)	index finger (2)

Right hand: index finger (2) on A♯, middle finger (3) on C♯, ring finger (4) on E, little finger (5) on G.

Left hand: little finger (5) on A♯, ring finger (4) on C♯, middle finger (3) on E, index finger (2) on G.

A♯ Diminished 7th Inversions

Root position
A♯ – C♯ – E – G
1st inversion (A♯dim7/C♯)
C♯ – E – G – A♯
2nd inversion (A♯dim7/E)
E – G – A♯ – C♯
3rd inversion (A♯dim7/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:

D♭ Diminished 7th→E Diminished 7th→G Diminished 7th→

A♯ Diminished 7th : Frequently Asked Questions

What notes are in A♯dim7?

A♯dim7 contains A♯, C♯, E and G. The formula is 1, ♭3, ♭5, ♭♭7.

How do you play A♯dim7 on piano?

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

What are the inversions of A♯dim7?

4 positions: root position A♯ C♯ E G, A♯dim7/C♯, A♯dim7/E, A♯dim7/G.

What is the difference between A♯dim7 and A♯dim?

Drops G. 3 of the notes are shared.

What is an easy A♯dim7 for small hands?

The guide tones, ♭3 and ♭♭7 voicing, C♯4 G4, spans 6 semitones or about 83 mm.

What are the frequencies of A♯dim7?

From A♯3 at A440 in 12-TET: 233.08, 277.18, 329.63, 392.00 Hz.

What is the set class of A♯dim7?

Prime form (0369), Forte 4-28, interval vector <004002>.

How do I transpose A♯dim7 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♭.

Is B♭dim7 the same as A♯dim7?

Enharmonically yes: the same piano keys and the same sound, spelled differently.

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	A♯3 C♯4 E4 G4	9	124 mm	none	identical
Close, first inversion	C♯4 E4 G4 A♯4	9	124 mm	none	identical
Close, second inversion	E4 G4 A♯4 C♯5	9	124 mm	none	identical
Close, third inversion	G4 A♯4 C♯5 E5	9	124 mm	none	identical
Drop 2	E3 A♯3 C♯4 G4	15	206 mm	none	identical
Drop 3	C♯3 A♯3 E4 G4	18	248 mm	none	identical
Drop 2 and 4	A♯2 E3 C♯4 G4	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	A♯2 G3 C♯4	15	206 mm	omits E	subset
Guide tones, ♭3 and ♭♭7	C♯4 G4	6	83 mm	omits A♯ and E	subset
Rootless close	C♯4 E4 G4	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♯	A♯3, C♯4, E4, G4	7	9	124 mm
First inversion: A♯dim7/C♯	C♯	C♯4, E4, G4, A♯4	6/5	9	124 mm
Second inversion: A♯dim7/E	E	E4, G4, A♯4, C♯5	4/3	9	124 mm
Third inversion: A♯dim7/G	G	G4, A♯4, C♯5, E5	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
A♯dim	drops G	1 ♭3 ♭5	3
A♯m7♭5	G becomes G♯	1 ♭3 ♭5 ♭7	3
A♯m6	E becomes E♯	1 ♭3 5 6	3
A♯m	E, G becomes E♯	1 ♭3 5	2
A♯m7	E, G becomes E♯, G♯	1 ♭3 5 ♭7	2
A♯mMaj7	E, G becomes E♯, G×	1 ♭3 5 7	2
A♯6	C♯, E becomes C×, E♯	1 3 5 6	2

Frequencies

Note	MIDI	Frequency
A♯3	58	233.08 Hz
C♯4	61	277.18 Hz
E4	64	329.63 Hz
G4	67	392.00 Hz

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

Set theory: prime form, Forte number, interval vector

Absolute pitch class set: {10, 1, 4, 7}
Normal order: [1, 4, 7, 10]
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