Mystical, Compassionate, Tragic
Tone in a novel generally means the feel of the book, or in other words, the kind of emotions it produces with its language. And since Cry, the Beloved Country uses its deeply sad subject matter to create a political point, we can see why there would be a lot of raw emotion in this book. How does Alan Paton make the language of this book so sorrowful? Let's look at a passage from the last chapter, when Kumalo is meditating on top of a mountain while waiting for his son's execution.
Why was it given to one man to have his pain transmuted into gladness? Why was it given to one man to have such an awareness of God? And why might not another, having no such awareness, live with pain that never ended? […] But his mind would contain it no longer. It was not for man's knowing. He put it from his mind, for it was a secret. (3.36.43-44)
Here, Kumalo is wrestling with some big questions. In fact, these are the biggest questions: why is it that some people have a happy ending while others don't? Why is it that some people maintain faith in God, while others do not find their answers in religion? Instead of answering these giant questions with some easy reply, the novel tells us that this kind of stuff is "not for man's knowing" (3.36.44). The religious nature of these questions gives the book a mystical tone, meaning that the book deals with ambiguous, often deeply spiritual material.
So this passage tells us that there are things that we not only do not know, but that we also cannot know, because they are beyond human understanding. By leaving the reader in a state of uncertainty about why all of these terrible things have happened to the Kumalo family and whether the future will be any better, Cry, the Beloved Country inspires a sense of anxiety and concern for its central characters and their social situations.
We want to try to change things—to help as best we can. That's why we say that the tone of the book is compassionate. It produces a sense of sympathy in the reader because we know that the main characters are suffering so much confusion and doubt.
But there's is also a sense of tragedy throughout this passage. Even though Kumalo spends much of the final chapter giving thanks for all of the good things in his life, he knows that many people do not have their "pain transmuted into gladness." In other words, while Kumalo feels that he has been saved, many others remain in pain.
And not only are other people outside of the novel continuing to suffer, but Kumalo himself is about to lose his only child. Absalom is about to be executed for Pete's sake. We admire Kumalo's resolution to be grateful and to avoid despair at the end of Cry, the Beloved Country. But it almost makes it sadder for us that Alan Paton doesn't linger on some melodramatic scene of Kumalo's tears and misery. Kumalo's patience and dignity in the face of his great suffering give the book a deeply tragic tone.