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

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