Asus2: A Suspended 2nd Piano Chord

Root position: either hand, fingers low note to high
Hand	Notes	Fingers
Right	A, B, E	1-3-5
Left	A, B, E	5-3-1

Scale degree, note, and interval measured from the root.
Degree	Note	Interval from root	Semitones
1	A	Perfect unison	0
2	B	Major second	2
5	E	Perfect fifth	7

Construction

A Suspended 2nd = Root + Major 2nd + Perfect 5th = A, B, E

Note	Interval	Degree
A	Root	1
B	Major 2nd	2
E	Perfect 5th	5

Fingering

Note	Key color	Right hand	Left hand
A	white	thumb (1)	little finger (5)
B	white	middle finger (3)	middle finger (3)
E	white	little finger (5)	thumb (1)

Right hand: thumb (1) on A, middle finger (3) on B, little finger (5) on E.

Left hand: little finger (5) on A, middle finger (3) on B, thumb (1) on E.

A Suspended 2nd Inversions

Root position
A – B – E
1st inversion (Asus2/B)
B – E – A
2nd inversion (Asus2/E)
E – A – B

Key Signature

A Suspended 2nd 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

Scales That Include the A Suspended 2nd

C Major (vi)
G Major (ii)
D Major (V)
A Major (I)
E Major (IV)
A Minor (i)
E Minor (iv)
B Minor (VII)

Same Notes, Other Names

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

E Suspended 4th→

A Suspended 2nd : Frequently Asked Questions

What notes are in Asus2?

Asus2 contains A, B and E. The formula is 1, 2, 5.

How do you play Asus2 on piano?

Play A, B and E together. Right hand fingers 1, 3, 5; left hand 5, 3, 1. Every note is a white key.

What are the inversions of Asus2?

3 positions: root position A B E, Asus2/B, Asus2/E.

What is the difference between Asus2 and Aadd9?

Adds C♯. 3 of the notes are shared.

What is an easy Asus2 for small hands?

The root and third only voicing, A3 B3, spans 2 semitones or about 28 mm.

What are the frequencies of Asus2?

From A3 at A440 in 12-TET: 220.00, 246.94, 329.63 Hz.

What is the set class of Asus2?

Prime form (027), Forte 3-9, interval vector <010020>.

How do I transpose Asus2 to another key?

Keep the 1, 2, 5 formula on the new root. Csus2 is C, D, G; C♯sus2 is C♯, D♯, G♯.

A Suspended 2nd 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 B3 E4	7	96 mm	none	identical
Close, first inversion	B3 E4 A4	10	138 mm	none	identical
Close, second inversion	E4 A4 B4	7	96 mm	none	identical
Open, fifth on top	A2 E3 B3	14	193 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	Fit
Root and third only	A3 B3	2	28 mm	omits E	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, B3, E4	5/3	7	96 mm
First inversion: Asus2/B	B	B3, E4, A4	6/3	10	138 mm
Second inversion: Asus2/E	E	E4, A4, B4	6/4	7	96 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
Aadd9	adds C♯	1 3 5 9	3
A	B becomes C♯	1 3 5	2
Am	B becomes C	1 ♭3 5	2
Asus4	B becomes D	1 4 5	2
Amaj7	B becomes C♯, G♯	1 3 5 7	2
A7	B becomes C♯, G	1 3 5 ♭7	2
Am7	B becomes C, G	1 ♭3 5 ♭7	2
AmMaj7	B becomes C, G♯	1 ♭3 5 7	2
A7sus4	B becomes D, G	1 4 5 ♭7	2
A6	B becomes C♯, F♯	1 3 5 6	2
Am6	B becomes C, F♯	1 ♭3 5 6	2
Adim	B, E becomes C, E♭	1 ♭3 ♭5	1

Frequencies

Note	MIDI	Frequency
A3	57	220.00 Hz
B3	59	246.94 Hz
E4	64	329.63 Hz

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

Set theory: prime form, Forte number, interval vector

Absolute pitch class set: {9, 11, 4}
Normal order: [9, 11, 4]
Prime form: (027)
Forte number: 3-9
Interval vector: <010020>

Pair	Interval	Semitones	Interval class
A to B	Major second	2	2
A to E	Perfect fifth	7	5
B to E	Perfect fourth	5	5

Where these facts come from

Every value on this page is derived from the note formula for a suspended 2nd 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 Suspended 2nd

Fingerings

A Suspended 2nd: notes and degrees