The A Major 9th chord is a five-note chord made up of A, C♯, E, G♯, and B. It is built from a root, major third, perfect fifth, major seventh, and major ninth.
Construction
A Major 9th = Root + Major 3rd + Perfect 5th + Major 7th + Major 2nd = A · C♯ · E · G♯ · B
| Note | Interval | Degree |
|---|---|---|
| A | Root | 1 |
| C♯ | Major 3rd | 3 |
| E | Perfect 5th | 5 |
| G♯ | Major 7th | 7 |
| B | Major 2nd | 9 |
Key Signature
A chord has no key signature of its own, but the A Major 9th is the tonic (I) chord of A Major, whose key signature has 3 sharps (F♯, C♯, G♯).
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 triads built on each degree of the A major scale:
A Major 9th — Frequently Asked Questions
What is the A Major 9th chord on piano?
The A Major 9th chord contains the notes A – C♯ – E – G♯ – B. On piano, play these notes together to sound the chord.
What notes are in the A Major 9th chord?
The A Major 9th chord (Amaj9) contains five notes: A (root), C# (major third), E (perfect fifth), G# (major seventh), and B (major ninth). It is Amaj7 with an added ninth.
How does Amaj9 differ from A9?
Amaj9 has a major seventh (G#). A9 has a minor seventh (G). Amaj9 is dreamy; A9 is dominant and bluesy.
How is Amaj9 used in music?
Amaj9 is a lush tonic in A Major. It appears in folk-jazz, acoustic music, and contemporary worship where A Major is a common key.
What songs use Major 9th chords?
Major 9th chords appear in neo-soul, jazz, and lo-fi. Amaj9 is common in acoustic and worship settings.
How does Amaj9 differ from Aadd9?
Amaj9 includes the major seventh (G#). Aadd9 has no seventh.
Do I need to play all five notes?
No — drop the fifth: A–C#–G#–B is the practical voicing.