B 7/G#
The B 7 chord consists of the B (Perfect unison), D# (Major third), F# (Perfect fifth) and A (Minor seventh) notes, with G# as the bass note.

How to play the B 7/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# (Perfect fifth) — 7 semitones above B
- Add A (Minor seventh) — 10 semitones above B
- Press all 5 notes simultaneously to sound the B 7/G# chord