C b5
The C b5 chord consists of the C (Perfect unison), E (Major third) and F# (Diminished fifth) notes.

How to play the C b5 chord
- Find C (Root) on the piano keyboard
- Add E (Major third) — 4 semitones above C
- Add F# (Diminished fifth) — 6 semitones above C
- Press all 3 notes simultaneously to sound the C b5 chord