G Viennese trichord/C
The G Viennese trichord chord consists of the G (Perfect unison), G# (Minor second) and C# (Diminished fifth) notes, with C as the bass note.

How to play the G Viennese trichord/C chord
- Play C as the lowest bass note in the left hand
- Find G (Root) on the piano keyboard
- Add G# (Minor second) — 1 semitone above G
- Add C# (Diminished fifth) — 6 semitones above G
- Press all 4 notes simultaneously to sound the G Viennese trichord/C chord