F# 3/B
The F# 3 chord consists of the F# (Perfect unison) and A# (Major third) notes, with B as the bass note.

How to play the F# 3/B chord
- Play B as the lowest bass note in the left hand
- Find F# (Root) on the piano keyboard
- Add A# (Major third) — 4 semitones above F#
- Press all 3 notes simultaneously to sound the F# 3/B chord