Enharmony
The ability to write the same pitch in many ways is called enharmony. F# and Gb are enharmonic.
Accidentals
A letter is natural, sharp or flat.
The letter is natural unless otherwise indicated.
Ab (flat) is a semitone lower than A natural.
A# (sharp) is a semitone higher than A natural.
 |  |  |
| Flat | Natural | Sharp |
| Ab | A | A# |
A word of caution. In text the accidental follows the letter, as in Ab and A#. On the stave the accidental precedes the note head.
Watch your step!
C# is Db. E# is not Fb.
Remember, C to D is a tone and E to F is a semitone.
While C# is Db, E# is F and Fb is E. Beginners and advanced students often trip-up on this fact.
| Gb | G | G# | ||||||||||||
| Fb | F | F# | Ab | A | A# | |||||||||
| Cb | C | C# | Eb | E | E# | Bb | B | B# | ||||||
| Db | D | D# | Cb | C | C# | |||||||||
| ½ | ½ | ½ | ½ | ½ | ½ | ½ | ½ | ½ | ½ | ½ | ½ | ½ | ½ | ½ |
Draw the keyboard for the pattern.
| C# Db | D# Eb | F# Gb | G# Ab | A# Bb | ||||||||||||
C B# | D | E Fb | F E# | G | A | B Cb | ||||||||||
Double flats and double sharps
Double flats and double sharps are accidentals for special occasions. A double flat is a semitone lower than flat. A double sharp is a semitone higher than sharp.
 | | | |  |
| double flat | flat | natural | sharp | double sharp |
The complete set of accidentals and their enharmonic equivalents follows.
| Bx C# Db | D# Eb Fbb | Ex F# Gb | G# Ab | A# Bb Cbb | ||||||||||||
| B# C Dbb | Cx D Ebb | Dx E Fb | E# F Gbb | Fx G Abb | Gx A Bbb | Ax B Cb | ||||||||||