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

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