DIATONIC SCALE:

The diatonic scale ascends and descends entirely by notes proper to the key and or uses notes proper to the prescribed 7 tone major or minor scale eg. The diatonic structure for the G Major scale is "G A B C D E F# G" with the F# appearing in the key signature. The diatonic structure for E melodic minor includes the sharpened 6th and 7th (ascending accidentals) as notes being proper to the scale, even though not appearing in the key signature with the F#. The same can be said for the diatonic structure of the E harmonic minor with the sharpened 7th (ascending & descending accidental) not appearing in the key signature with the F#. Any additional, altered or deviation in or to a diatonic scale is referred to purely as an accidental and may be included in the construction of a diatonic scale or invention of a mode for particular musical use.