Nature's pattern-book, too, is full of half tones and mixed tints.
Think of the half tones as part of the lights and not as part of the shadows.
They mostly comprise only a few tones, at the most an octave, and are sung in half tones, ascending in different keys.
It was a phrase of song, a wandering strain in half tones and fluted accidentals, not unmelodious.
There are no half tones, no subtle interblending of different currents of thought.
Try and arrange it so that the tone of the ground of your cast comes about equal to the half tones in the relief.
Taking raw umber and white (oil paint), mix up a tone that you think equal to the half tones of the cast before you.
Note carefully where the light masses come sharply against the half tones and where they merge softly into them.
But I do not think there is any rule to be observed here: there are too many exceptions, and no mention is made of half tones.
Single songs vary from half a tone to three and a half tones, averaging one and a half.