A add9
The A add9 chord consists of the A (Perfect unison), C# (Major third), E (Perfect fifth) and B (Major ninth) notes.

How to play the A add9 chord
- Find A (Root) on the piano keyboard
- Add C# (Major third) — 4 semitones above A
- Add E (Perfect fifth) — 7 semitones above A
- Add B (Major ninth) — 14 semitones above A
- Press all 4 notes simultaneously to sound the A add9 chord