And why so many Christian preachers use a very sing song tone (and even sing in some traditions).
[0] https://www.youtube.com/watch?v=0JPRvxTjfOk
It's in our speech all the time. Preachers do exaggerate it. As do politicians and comedians, for example. But Diana pulls it right out of her own speech, and demonstrates that even children instantly recognize the musicality of it as soon as the bit of speech is repeated.