I look at every note, chord, accidental, tone, no matter as being chromatic, I use non-diatonic to describe the chromatic tones used but not diatonic to a given scale or key, because the notes that are diatonic to any given scale or key are also included in the chromatic scale.

I look at every note, chord, accidental, tone, no matter as being chromatic, I use non-diatonic to describe the chromatic tones used but not diatonic to a given scale or key, because the notes that are diatonic to any given scale or key are also included in the chromatic scale. I recognize that both terms are used somewhat interchangeably, but I feel it can actually lead to confusion for the student who is not yet accustomed to actual practices between musicians.