A Add 9
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Aadd9
A – C♯ – E – B
Formula:R-M3-P5-M9
Intervals:P1-M3-P5-M9
Scale Degrees:1-3-5-9
Introduction
The A Add 9 chord is a four-note chord made up of A, C♯, E, and B. It is built from a root, major third, perfect fifth, and major ninth.
Notes
A Add 9 Inversions
| Position | Notes |
|---|---|
| Root Position | A – C♯ – E – B |
| 1st Inversion | C♯ – E – A – B |
| 2nd Inversion | E – A – B – C♯ |
| 3rd Inversion | A – C♯ – E – B |
Key Signature
The key of A Add 9 has 3 sharps.
F♯C♯G♯
Order of sharps
Sharps are added to a key signature in a fixed order. Each new sharp key adds the next sharp on the list.
F♯C♯G♯D♯A♯E♯B♯
Mnemonic: Father Charles Goes Down And Ends Battle
Chords in the Key of A Major
These are the diatonic triads built on each degree of the A major scale:
C
D
E
F
G
A
B
C
D
E
F
G
A
B
I — A Major (major)
Theory: Intervals
Formula: R-M3-P5-M9
Intervals: P1-M3-P5-M9
The A Add 9 is built by stacking intervals from the root note. The formula R-M3-P5-M9 describes the scale degrees used. The intervals P1-M3-P5-M9 show the distance between each note in the chord.
A Add 9 — Frequently Asked Questions
What notes are in the A Add 9 chord?
The A Add 9 chord (Aadd9) contains four notes: A (root), C# (major third), E (perfect fifth), and B (major ninth). No seventh — the ninth adds brightness to the triad.
How does Aadd9 differ from A9?
Aadd9 has no seventh. A9 includes the minor seventh (G). Aadd9 is bright and open; A9 is dominant and bluesy.
How is Aadd9 used in music?
Aadd9 substitutes for A Major in pop, rock, and country. A Major is one of the most common guitar keys, making Aadd9 a frequent voicing in acoustic arrangements.
What songs use add9 chords?
Add9 chords appear in Wonderwall (Oasis), Good Riddance (Green Day), and countless acoustic pop songs. Aadd9 is common in country and folk-rock.
How does Aadd9 differ from Asus2?
Both contain A and B. Aadd9 keeps C# (major third); Asus2 replaces it. Aadd9 is major with colour; Asus2 is ambiguous.
Can I substitute Aadd9 for A Major?
Yes — Aadd9 replaces A Major in most pop and acoustic contexts for added shimmer.
Practice Tips
- Play A Major then add B above — hear the bright, open shimmer.
- Aadd9 is common in acoustic and country music — practice it as your default A voicing.
- Compare Aadd9 with Asus2 — the major third (C#) gives add9 its clear major quality.
- Try Dadd9 → Aadd9 for a warm acoustic pop progression.
- Practice Aadd9 with B on top for maximum brightness.
- Aadd9 has a satisfying hand shape — the B sits naturally above the A Major triad position.
Related Tools
Chord FinderLook up any chord — see the notes, hear it, and play along.Chord DrillTimed drills to build speed and recognition across all chord types.Practice RoomPlug in a MIDI keyboard and get real-time feedback on every chord and scale.Circle of FifthsVisualize key relationships, relative minors, and key signatures.MIDI MonitorLive MIDI message stream with note names, velocity, and a scrolling staff.