Speakers have many tools at their disposal for building vocal variety:
Volume. Volume adds variety to whatever you say.
Practice: Say the word no over and over, starting very softly (almost whispering) and working your way to very loud (almost shouting).
Pitch and Inflection. Different from volume, pitch and inflection reflect your overall tone.
Practice: Say the following, letting your voice follow the words: "Let your voice come down evenly, smoothly as a sigh. Then evenly up and ever so high. Hold our tones level and high today; then level and low tomorrow, I say. Let tones glide high, then slide down low. Learn to say, "no, no, NO." Recite the "do, re, mi" scale, going from a high tone to a low one. Or try the numbers one through eight, going up the scale and coming down again.
Pace and Rhythm. How fast or slow you articulate the words and sounds.
Practice: Read a rhyme such as "The Ballad of Green Broom." Slow down each time you say, "Broom, Green Broom" and the words that rhyme with it. Read the rest very quickly.
Emphasis. This affects your word and syllable stress. The key point is to be sure people get your main ideas. Help them by subverting the less important ones. A common fault of speakers is to emphasize too many things; you should isolate the key points you want to emphasize.
Practice: Use a simple declarative statement such as, "I am going to the store." Use the same sentence to answer a series of questions, emphasizing the appropriate word to answer the question. Subvert the unimportant words.
Many Americans have the bad habit of fading away at the end of a sentence. This can be dangerous in certain situations. Imagine you were given the task of diffusing a bomb, and the person giving you instructions says, "Whatever you do, don't touch the...." That last word could be a lifesaver! Although the last word is not always that dramatically important, it doesn't mean you should just let it drop out of hearing altogether.
Attitude. The same word or phrase can take on radically different meanings, depending on the attitude implicit in your voice.
Practice: Say well as if you were: annoyed, disgusted, surprised, thrilled, in doubt, suspicious, thoughtful, and pugnacious
The Pause. Powerful speakers use the pause several ways—for emphasis, effect, and mood. Pauses can be long, medium, short, or very short (when you're just drawing a breath). They can also signal a transition.
There are four types of pauses:
The Think About it Pause: Gives people a chance to digest what you have said (one to two beats long). It can be effective to pause before you deliver an important point, although it's not good if it's so overused that it becomes boring.
Transitional Pause: Take a short pause between two minor points (one beat) and a longer pause (two to two and a half beats) for transitions between two more important points.
Emphasis Pause: Take a long pause before you make a statement or ask a question where you want people to think about the implications and meaning of what you have just said (two to three beats).
Pregnant Pause: Similar to the thinking pause, but used most often to create effect (two to three beats).
Practice: The next time you have to deliver good news, practice your pause. "Wait until I tell you the good news!" Stop. Count to three slowly. You'll sense the anticipation in your listeners. Enjoy it and feel its power. Then tell them the news.