G# dim/C
The G# dim chord consists of the G# (Perfect unison), B (Minor third) and D (Diminished fifth) notes, with C as the bass note.

How to play the G# dim/C chord
- Play C as the lowest bass note in the left hand
- Find G# (Root) on the piano keyboard
- Add B (Minor third) — 3 semitones above G#
- Add D (Diminished fifth) — 6 semitones above G#
- Press all 4 notes simultaneously to sound the G# dim/C chord