G# b5/D##
The G# b5 chord consists of the G# (Perfect unison), B# (Major third) and D (Diminished fifth) notes, with D## as the bass note.

How to play the G# b5/D## chord
- Play D## as the lowest bass note in the left hand
- Find G# (Root) on the piano keyboard
- Add B# (Major third) — 4 semitones above G#
- Add D (Diminished fifth) — 6 semitones above G#
- Press all 4 notes simultaneously to sound the G# b5/D## chord