The D♯ Add 9 chord is a four-note chord made up of D♯, F♯♯, A♯, and E♯. It is built from a root, major third, perfect fifth, and major ninth.
Construction
| Note | Interval | Degree |
|---|---|---|
| D♯ | Root | 1 |
| F♯♯ | Major 3rd | 3 |
| A♯ | Perfect 5th | 5 |
| E♯ | Major 2nd | 2 |
D♯ Add 9 Inversions



| Position | Notes |
|---|---|
| Root Position | D♯ – F♯♯ – A♯ – E♯ |
| 1st Inversion | F♯♯ – A♯ – E♯ – D♯ |
| 2nd Inversion | A♯ – E♯ – D♯ – F♯♯ |
| 3rd Inversion | E♯ – D♯ – F♯♯ – A♯ |
Key Signature
A chord has no key signature of its own, but the D♯ Add 9 is the tonic (I) chord of D# Major, whose key signature has 3 flats (B♭, E♭, A♭).
Order of flats
Flats are added in a fixed order — the reverse of the sharp order. Each new flat key adds the next flat on the list.
Mnemonic: Battle Ends And Down Goes Charles’ Father
Chords in the Key of D♯ Major
These are the triads built on each degree of the D♯ major scale:
Same Notes, Other Names
The notes D♯ – F♯♯ – A♯ – E♯ aren’t exclusive to this chord. Depending on which note is the bass and how the chord functions, the same pitches also spell: