We refer to contrast blending as a technique to blend several differently exposed (exposure bracketed) images in order to achieve a higher Dynamic Range.
However, contrast blending can be done completely 'by hand' as described on Michael Reichmann's site - http://www.luminous-landscape.com/tutorials/digital-blending.shtml
Here is a user comment on Michael's technique:
"I use the second technique, the Layer Mask approach, and have found that it works quickly and easily, while still leaving much room for tweaking as necessary. The only change I've made in my approach is at the end where I work in Levels instead of curves. I find that sliding the mid-tones to the right helps make the resulting image look more realistic. In some cases, you just have to play around with all three sliders until you get a good blend. I also will reduce the opacity of the top layer down to about 85% as well."
Mark Fink www.northernlight.net