I have been experimenting and investigating the role of dark tones vs. mid and light tones. Castagnet is very interesting in how he uses darks to "explain" his painting content. My tiny little sketch tried this out, playing around with some of his approach to passionate brushstrokes, while also letting the paint talk for itself (as it were). Tom Hoffmann is also interesting in how he interrogates the dark layer/passage/calligraphy and to what extent those darks are responsible for defining the content of the painting, and restraining the darks to only what is necessary.
As an aside, my sketch is a too Castagnet derivative, and was not trying to be a finished painting, but an exercise to understand the role of darks.
Perhaps you would all like to comment, debate and share what you think the role of darks are. To add to the discussion, perhaps you can also share when you think darks are overdone (both in tone and in emphasis)?