As you are probably aware, western music uses the letter names A B C D E F G to describe notes. If you look at the guitar though, you can see that an octave (from open string � to string � fret 12 for example) is actually divided into 12 different notes – each fret producing a different note.

If you play the open E string � then play the note at fret 1, the pitch rises. This rise in pitch is called a ‘semitone’. If you continue this up the string, after 12 semitones you reach the octave E at fret 12.

So on the guitar, moving your finger along a string by one fret (which is the same as shortening the length of the string by one fret) raises the pitch by a semitone. If you move your finger along by two frets, the pitch is raised by two semitones. Two semitones is equal to one ‘tone’.

In order to name these 12 notes we need to add to the seven letter names A B C D E F G. This is done by using ‘sharps’ (#) and ‘flats’ (b). The 12 semitones along your E string � are named like this:

A sharp raises the pitch of a note by a semitone. A flat lowers the pitch by a semitone. Clearly F sharp for example, is the same note as G flat. When a note has two names like this the notes are said to be enharmonic.