C# 13b9 Chord
How the C# 13b9 chord is built: its notes, its interval structure, and where it fits.
The C# 13b9 chord contains 6 notes: C# – D – F – G# – A# – B. It belongs to the thirteenth family of chord qualities. Like every chord, it is defined by the distances (intervals) between its notes, not by any one instrument — which is why the same formula names the chord whether it is voiced on a fretboard, a keyboard, or a choir.