:The last two rows are shaded, indicating keys that are generally avoided, inpart because they use inconvenient
enharmonic notes, denoted with "*". :In the standard tuning system of
12 equal temperament, the key of
C major, with 7 flats is enharmonically equivalent with
B major, which only requires 5 sharps. The order of flats in key signatures is : B♭, E♭, A♭, D♭, G♭, C♭, F♭ The corresponding order of keys also follows the
circle of fifths sequence: : F, B♭, E♭, A♭, D♭, G♭, C♭ Starting with no flats or sharps (C major), adding the first flat (B♭) indicates
F major; adding the next (E♭) indicates B♭ major, and so on, backwards through the circle of fifths. Some keys (such as C♭ major with seven flats) may be written as an enharmonically equivalent key (B major with five sharps in this case). In rare cases the flat keys may be extended further: : F♭ → B → E → A → D → G → C requiring double flats in the key signature. These are generally avoided as impractical, and the simpler enharmonic key signature is used instead. This principle applies similarly to the sharp keys. The staff below shows a key signature with three flats (
E major or its
relative minor C minor), followed by a note with a flat preceding it: The flat symbol placed on the note indicates that it is a D♭. :{ \omit Score.TimeSignature \relative c'' { \key es \major des1 } } In standard 12 tone equal temperament tuning, lowering a note's pitch by a semitone results in a note that is
enharmonically equivalent to the adjacent named note. In this system, B and A are considered to be equivalent. In other, non-standard
tuning systems, however, this is not the case. == Accidentals ==