The narrator's tone in Brave New World is satirical, using devices such as irony and oxymoron to draw the reader's attention to the troubling directions "progress" can take. Often, the narrator will simply provide context for something a character states. And, in providing that context, the narrator undermines the legitimacy of propaganda:
‘Yes, everybody’s happy now,’ echoed Lenina. They had heard the words repeated a hundred and fifty times every night for twelve years.
In a way, the narrator fact-checks Lenina in this passage, keeping their tone fairly consistent and informative while giving the reader the tools to understand how propaganda and brainwashing operate. The narrator's statement provides necessary context for Lenina's, reminding the reader that, while this character may believe everyone is happy, her belief is neither logical nor reflective of progress. If happiness can only be achieved through total societal control, then it is not an organic happiness. The "happiness" these people feel is the flat, hollow happiness of inebriation—it is two-dimensional and directionless. Simply by reminding the reader, in a straightforward and informative tone, of the reality of Lenina's situation, the narrator counteracts the effects of propaganda.