Thank you for taking the time to put together this article. It is a good introduction to using a single light source to produce different lighting styles. I'll certainly be recommending that new photographers wanting to start doing portraiture read it.
Once you understand the light and shadow effects you can achieve with a single light source then you are well on your way to understanding all lighting. Only by understanding the light illuminates and shadows define can you master lighting. .
All lighting setups start with a single main or key light. Additional light sources are only used to modify that main or key light, i.e. to modify the light and shadows. Learning single lighting is the key to learning lighting in general.
Thanks again for a very nice article.