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

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