The seven letters of the musical alphabet by themselves do not represent all the pitches in the tonal system. Between a pitch name and its repetition as you move up or down the staff are actually 12 pitches. Special symbols called sharps and flats along with notes are used to notate the other pitches. These two symbols along with another special symbol (the natural) are shown below. These symbols are also known as accidentals.
A sharp is used to raise a pitch name by a half step and a flat is used to lower a pitch name by a half step. A half step is the distance between each adjacent pitch. The sharp or flat symbol is placed in front of the note to which it refers. The natural symbol in front of a note returns the pitch to the normal pitch name.
The two staffs below show how each of the 12 pitches can be notated by using either sharps or flats with the seven notes of the musical alphabet. The pitches as shown make the "A" chromatic scale.
The distance between the adjacent pitches B and C is a half step, and the pitches E and F is a half step.
The distance between each of the other adjacent pitch names (without accidentals)
A and B; C and D; D and E; F and G; and G and A is two half steps. (Two half steps equals one whole step.)
Some notes shown below are enharmonic-they have the same pitch but different names:
A# = Bb; C# = Db; D# = Eb; F# = Gb; and G# = Ab.
When an accidental is placed before a note, all sebsequent notes of the same pitch are affected until changed by another accidental or until a bar line is passed. The verticle lines in the example below are bar lines. The areas between bar lines are called measures.
Two other accidentals are used. They are the double sharp and the double flat. The double sharp raises a note two half steps and a double flat lowers a note two half steps. In the example below notice that Dbb and C are enharmonic. They are notated different but have the same sound. In addition, Dx and E are enharmonic, Cb and B are enharmonic, and B# and C are enharmonic.