G# m9/B
The G# m9 chord consists of the G# (Perfect unison), B (Minor third), D# (Perfect fifth), F# (Minor seventh) and A# (Major ninth) notes, with B as the bass note.

How to play the G# m9/B chord
- Play B as the lowest bass note in the left hand
- Find G# (Root) on the piano keyboard
- Add B (Minor third) — 3 semitones above G#
- Add D# (Perfect fifth) — 7 semitones above G#
- Add F# (Minor seventh) — 10 semitones above G#
- Add A# (Major ninth) — 14 semitones above G#
- Press all 6 notes simultaneously to sound the G# m9/B chord