Toastmasters Champion Darren Flemming, from Australia, presents examples of voice variety. He was presenting a Workshop in Las Vegas, and gave me the permission to insert in our blog his teachings and videos, of course, with a link to the original.
Of course, there is more to it, and as our Founder, Ralph Smidley wrote in his book, printed in 1947 about Voice, the most important thing is to have a friendly voice! Clear enunciation, and variety helps a lot to the message, too.
In our manual, Competent Communicator, we have a whole project devoted to Voice Variety, to make us aware of its importance and practice it. Not only then, but every time from then on when we speak in public and also in private.
When you speak with courage and conviction, authenticity and passion, the voice follows without thinking. But even then, it is useful to make pauses and let the audience absorb what you have said, or pause before, let them look at you with suspense, wondering what will come.