C# dim7
The C# dim7 chord consists of the C# (Perfect unison), E (Minor third), G (Diminished fifth) and A# (Major sixth) notes.

How to play the C# dim7 chord
- Find C# (Root) on the piano keyboard
- Add E (Minor third) — 3 semitones above C#
- Add G (Diminished fifth) — 6 semitones above C#
- Add A# (Major sixth) — 9 semitones above C#
- Press all 4 notes simultaneously to sound the C# dim7 chord