The other way to increase local contrast in the midtone and highlight tonal range and not exceed the paper's exposure scale is through unsharp masking. Since this is proportional to camera negative density, it tends to bring shadow density upward and tend to leave highlight density as it exists.
I find the "unsharp mask" interesting, but I don't understand exactly how it works, or how noticable the effect/improvement is in practice.

Does anyone have a gallery image example where an unsharp mask was used? And/or even better, a masked/unmasked set for comparison?