Cflat

C-flat is the musical note that is a semitone lower than C. It is written with a flat accidental applied to the note C, shown as C♭. In equal temperament, C♭ functions as the same pitch as B natural; their frequencies are the same within octaves, so C♭ in a given octave is enharmonically equivalent to B in that octave (for example, C♭4 is about 246.94 Hz).

In theory, C-flat appears in various contexts of notation and harmony. The major scale built on C-flat, C-flat major, would spell the notes C♭, D♭, E♭, F♭, G♭, A♭, B♭, C♭ and would require seven flats in the key signature. Because of its heavy flat notation, C-flat major is primarily a theoretical construct; its enharmonic equivalent is B major, which has five sharps and is more common in practice. The related minor key would be C-flat minor, another extremely flat-intensive key that is rarely used in standard repertoire.

The primary purpose of using C♭ in notation is to preserve proper letter naming and diatonic order when a passage or modulation requires the scale degrees to remain spellings with C as the tonic. This helps maintain consistent interval structures and chord spellings within a piece, even when the audible pitch matches a more common enharmonic pitch class.

See also: B major, C-sharp major, enharmonic equivalence.