F# 5/B
The F# 5 chord consists of the F# (Perfect unison) and C# (Perfect fifth) notes, with B as the bass note.

How to play the F# 5/B chord
- Play B as the lowest bass note in the left hand
- Find F# (Root) on the piano keyboard
- Add C# (Perfect fifth) — 7 semitones above F#
- Press all 3 notes simultaneously to sound the F# 5/B chord