Here are seven sentences you can use to practice vocal variety. Say each sentence several times, each time using different pitch, rhythm, and word emphasis.
Why aren't you all lying on the beach in Hawaii right now?
(Try this as if you were angry, then as if you were motivating your team.)
How many of you paid all of your income tax last year?
(How does the sentence change if you emphasize the word "all"?)
What would you do if you knew you only had one month to live?
(Say this in a slow, measured tone. Then repeat it at a faster pace, emphasizing the words "one month." See the difference?)
This occasion will go down in history.
(There are two interpretations to this statement: the "occasion" might be a happy one, or it could be a day of infamy. Convey the two different meanings using pitch, volume, and attitude.)
I'm going to tell you how you can make $25,000 in 25 minutes.
(Pauses can make this sentence quite effective. Where would you put them?)
I was told two years ago I had three months to live.
(Emphasis can bring out the contrast between the words "two years" and "three months.")
Let me tell you how I won the lottery!
(Use all the tools to vary this sentence in as many ways as possible.)