A semitone is the smallest interval available on the piano. If we play any note on the piano and then play a note directly above (to the right) or below (to the left) of that specific note, the new note will be a semitone away from the original note. The new note can be either white or black depending on the position of the original note. Notice that two black notes cannot form a semitone but two white ones can. In other words going from one black key to the closest black key always goes via a white key so the black keys are always at least 2 semitones apart.
Examples of semitones.
Semitones are very useful when constructing scales and/or chords. We can form certain formulas or patterns for each scale and/or chord by using semitones. For example the major scale has the following semitone pattern 2-2-1-2-2-2-1. By using that pattern we can then construct any major scale. For example we can construct the G major scale by starting on G and using the semitone pattern.
Constructing the G major scale using the semitones pattern. R stands for “root” which means the first note of the scale.
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