What's the most effective way to teach my child to adjust their tones? 

Recognizing patterns is what our brains do best. Finding and practicing Patterns-of-Tonalities is the best way to teach by experience.  Use the Mirroring game to achieve this. Before you play the game, tell your child one reason why it's worthwhile to learn Patterns-of-Tonalities. Studies showing the benefits, building a rapport through commonalities or emotional contagion are factors that can trigger your child, depending on the trigger. 

The ability to notice patterns of tonalities must be of value to us, so why should we care? In part, this is because mirroring tonalities creates rapport:

By adapting your tone, volume, pace, and rhythm for each context and person, you subconsciously build trust. According to theory, people prefer to be with people who are like them or whom they´d like to be like. And dislike those who are different. 

If you mention that this is not good for an argument, you prove your point: You prefer people who prefer an argument over people with different beliefs. 

Observing others in a public space is an excellent way to see this phenomenon in action. As they become more in tune with their talking partner, they will become more alike. Their movements will mimic one another. They hold their arms the same way, or when one leans forward, the other mirrors it. We use the language they use. Perhaps you adjust your voice tone. 

Imagine a fast talker meeting a slow talker. Both would be frustrated, one because the pace is too slow, the other because it is too fast. 

Then, how does mirroring work with patterns of tonality? 

Let's challenge our kids to recognize patterns in volume, tempo, and tone. Up until the point where the other person does not know it, they will just feel more connected to them. 

Read, discuss and offer suggestions in each of these three areas (volume, tone or tempo).  Make a drawing of the pattern. 

For instance. Speed. I will speak really fast (draw dots on the paper) and then really slowly. I will exaggerate at first, then move to small patterns. 

Volume: Normal, then whisper, then normal, then loud. 

Talk angry, happy, grateful, ask a question, give a command. Determine the tone for each. We'll cover several patterns next week. Today, start observing and drawing out the patterns.