G dim
The G dim chord consists of the G (Perfect unison), A# (Minor third) and C# (Diminished fifth) notes.

How to play the G dim chord
- Find G (Root) on the piano keyboard
- Add A# (Minor third) — 3 semitones above G
- Add C# (Diminished fifth) — 6 semitones above G
- Press all 3 notes simultaneously to sound the G dim chord