A9
A Dominant 9th — a dominant seventh widened with the ninth — fuller, funkier movement toward the resolution.
The keys
A – C♯ – E – G – B
What's inside A9
| Note | Interval from root | Degree |
|---|---|---|
| A | Root | 1 |
| C♯ | Major 3rd | 3 |
| E | Perfect 5th | 5 |
| G | Minor 7th | b7 |
| B | Major 9th | 9 |
A working voicing
Split the chord between two hands the way working players do — a solid shell low down, the colour tones up top:
| Hand | Keys |
|---|---|
| Left (shell) | A2 – G3 |
| Right (colour) | D♭5 – B5 |
Where A9 lives
As the I chord
A9 → D → E → A9
The classic I–IV–V–I motion with this chord as home.
In a ii–V–I
Bm7 → E7 → A9
The strongest cadence in harmony, resolving onto this chord.
Put A9 under your fingers
Hear every voicing, see the keys light up, and drill it in the interactive Chord & Voicing Lab.
Open the Chord & Voicing Lab →