key signature
C♭ major
C♭1D♭2E♭3F♭4G♭5A♭6B♭7
7 flats, written B♭ E♭ A♭ D♭ G♭ C♭ F♭
The chords that live in it
C♭degree 1 · majorD♭mdegree 2 · minorE♭mdegree 3 · minorF♭degree 4 · majorG♭degree 5 · majorA♭mdegree 6 · minorB♭dimdegree 7 · diminished
Built by stacking thirds inside the scale and asking what quality comes out, rather than from a table of roman numerals.
What is true of it
C♭ major has 7 flats.
They are written in this order, always: B♭ E♭ A♭ D♭ G♭ C♭ F♭.
Its notes are C♭, D♭, E♭, F♭, G♭, A♭ and B♭.
Relative: A♭ minor has the same 7 flats. Parallel: C♭ minor has 10 flats, which is why changing mode changes the signature by three.
Every key
G♭ majorD♭ majorA♭ majorE♭ majorB♭ majorF majorC majorG majorD majorA majorE majorB majorF♯ majorC♯ majorA♭ minorE♭ minorB♭ minorF minorC minorG minorD minorA minorE minorB minorF♯ minorC♯ minorG♯ minorD♯ minorA♯ minor