Intervals
If two notes sound different, one must be higher - the other lower. The distance between the sounds is referred to as an interval. The smallest interval is a semitone, on the guitar, one fret. Two frets or semitones make one tone. The note immediately above C is therefore C#, the next D and so on. On the guitar in the key of C major there are two frets between all of the notes excepting E and F and B and C.

Interval sizes are determined by counting the letters from the lowest up. C to E is C,D,E and is therefore a third. Any interval that is counted from the tonic of the major scale to another note in the scale is a perfect or major interval.

• If a major interval is reduced by a semitone it becomes a minor interval.
• If a minor interval by a semitone it becomes a diminished interval.
• If a major interval is increased by a semitone it becomes an augmented interval.
• If a minor interval is increased by a semitone it becomes a major interval.

Accidentals
Accidentals are symbols that represent a change to the pitch of a note, they can be sharps(#) that raise a note by one semitone, or a fret, and flats (b) that lower a note by a semitone and naturals that return a note back to its natural state.

In the diatonic Scale the interval between B and C, E and F is one semitone. The interval between all other intervals is a tone.
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