F maj11/C#
The F maj11 chord consists of the F (Perfect unison), A (Major third), C (Perfect fifth), E (Major seventh), G (Major ninth) and A# (Perfect eleventh) notes, with C# as the bass note.

How to play the F maj11/C# chord
- Play C# as the lowest bass note in the left hand
- Find F (Root) on the piano keyboard
- Add A (Major third) — 4 semitones above F
- Add C (Perfect fifth) — 7 semitones above F
- Add E (Major seventh) — 11 semitones above F
- Add G (Major ninth) — 14 semitones above F
- Add A# (Perfect eleventh) — 17 semitones above F
- Press all 7 notes simultaneously to sound the F maj11/C# chord