Every time you speak to another person, your tone of voice is either going to be similar to pleasant music or to distressful notes. When a person is frustrated or angry or overwhelmed, the tone of voice emits very different music than when a person is calm and serene, happy and joyful, kind and compassionate.
If someone would have to sing at his best professionally, regardless of how he felt a few minutes earlier, he knows that he has to put himself into the state of singing well. The more important the reason for singing well, the more motivated he would feel to do the best job he possibly could. That should be our attitude when speaking to another child of the Almighty. We are speaking in the presence of the Creator to one of His children. Speak with a tone of voice that is conducive to harmony with others.
(Growth Through Tehillim: Exploring Psalms for Life Transforming Thoughts, pp. 164-5)