For me, the key takeaway is simply to inject variety into the way you speak, variety based on the meaning you’re trying to convey. So many speakers forget this. They give a talk in which every sentence has the same vocal pattern. A slight rise at the start, and a drop at the end. There are no pauses or changes of pace. What this communicates is that no single part of your talk matters more than any other part. It’s just plodding its way along until it gets to the end. The biological effect of this is hypnotic. That is, it simply puts your audience to sleep.
