D# m11/C
The D# m11 chord consists of the D# (Perfect unison), F# (Minor third), A# (Perfect fifth), C# (Minor seventh), F (Major ninth) and G# (Perfect eleventh) notes, with C as the bass note.

How to play the D# m11/C chord
- Play C as the lowest bass note in the left hand
- Find D# (Root) on the piano keyboard
- Add F# (Minor third) — 3 semitones above D#
- Add A# (Perfect fifth) — 7 semitones above D#
- Add C# (Minor seventh) — 10 semitones above D#
- Add F (Major ninth) — 14 semitones above D#
- Add G# (Perfect eleventh) — 17 semitones above D#
- Press all 7 notes simultaneously to sound the D# m11/C chord