Bb maj13/F#
The Bb maj13 chord consists of the Bb (Perfect unison), D (Major third), F (Perfect fifth), A (Major seventh), C (Major ninth) and G (Major thirteenth) notes, with F# as the bass note.

How to play the Bb maj13/F# chord
- Play F# as the lowest bass note in the left hand
- Find Bb (Root) on the piano keyboard
- Add D (Major third) — 4 semitones above Bb
- Add F (Perfect fifth) — 7 semitones above Bb
- Add A (Major seventh) — 11 semitones above Bb
- Add C (Major ninth) — 14 semitones above Bb
- Add G (Major thirteenth) — 21 semitones above Bb
- Press all 7 notes simultaneously to sound the Bb maj13/F# chord