"And people will say: 'Let's hear about Frodo and the Ring!' And they'll say: 'Yes, that's one of my favorite stories. Frodo was very brave, wasn't he dad?' 'Yes, my boy, the famousest of the hobbits, and that's saying a lot.'"
"It's saying a lot too much," said Frodo, and he laughed, a long clear laugh from his heart. Such a sound had not been heard in those places since Sauron came to Middle-earth. To Sam suddenly it seemed as if all the stones were listening and the tall rocks leaning over them. But Frodo did not heed them; he laughed again. "Why Sam," he said, "to hear you somehow makes me as merry as if the story was already written. But you've left out one of the chief characters: Samwise the stouthearted. 'I want to hear more about Sam, dad. Why didn't they put in more of his talk, dad? That what I like, it makes me laugh. And Frodo wouldn't have got far without Sam, would he, dad?'" (4.8.63-4)
It's a credit to Frodo that he can laugh while sitting near Minas Morgul with the Ruling Ring on a chain around his neck, and it's equally to Sam's credit that he can tell a joke that makes Frodo chuckle. The obvious love between Frodo and Sam seems to be the only cure for the miseries of Mordor. And even the land itself seems to be tuning in, leaning over to hear their banter. This moment with Frodo's laugh is a rare instance when we stop to think of the agony it would be for the land itself—if it is alive in any sense, as it is being described here—to be tortured with the presence of the utter evil living in Mordor. Perhaps the rocks are listening to Frodo's laughter as their own cure for the miseries they have endured under Sauron.