C-flat major

C♭ major

Relative key	A♭ minor enharmonic: G♯ minor
Parallel key	C♭ minor enharmonic: B minor
Dominant key	G♭ major enharmonic: F♯ major
Subdominant	F♭ major enharmonic: E major
Enharmonic	B major
Component pitches
C♭, D♭, E♭, F♭, G♭, A♭, B♭, C♭

C♭ major is a major scale based on C♭, consisting of the pitches C♭, D♭, E♭, F♭, G♭, A♭, and B♭. Its key signature has seven flats.

C♭ major is the only major or minor key, other than theoretical keys, which has "flat" or "sharp" in its name, but whose tonic note is the enharmonic equivalent of a natural note (a white key on a keyboard instrument).

Its relative minor is A♭ minor (or enharmonically G♯ minor), and its parallel minor is C♭ minor, usually replaced by B minor, since C♭ minor's three double-flats make it generally impractical to use.

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Wikipedia