A key element in developing your voice is challenging it with thought patterns it isn't used to. It provides an expansion effect, which at first seems a bit unpleasant, because you are not used to it, but feels nice once it settles in the system.
It's the equivalent of trying a new physical exercise. You are mentally, emotionally and physically challenged during the exercise, but you reap the benefits of it afterwards.
In this combo exercise you are going to mix the earth element with the fire element to give your voice an expanded territory to play within.