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

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