Brain Wave (London, 1977) is descibed as "the change" in the text (Chapter 20, p. 172-173) and as "the Change" in the relevant Wiki article. Whether the word is capitalized elsewhere in the text I have not ascertained.
How many fictional "Changes" are there?
In The Days Of The Comet by HG Wells (see here);
The Change series by SM Stirling;
The Changes Trilogy by Peter Dickinson (see here).
Quoting from memory alone, I think that there is an exchange roughly like this in News From Nowhere by William Morris:
"'When the Change came - the revolution as we used to call it - was there violence?'
"'Of course there was violence. What peace was there among those poor wretches of the twentieth century?'"
(i) I started thinking about Wells' and Stirling's "Changes," then asked, "Does Anderson have one?" and of course he does.
(ii) Wells shows us a mad vicar before the Change but does not show us a Changed vicar later whereas Stirling does show us both mad and sane clergymen after his Change. However, Wells' narrator's mother modifies her religious views. She still believes that there is a Hell, just that no one goes there!
(iii) Again quoting from memory, someone said that revolutionary violence results from conservatism. People cling to outmoded social relationships long after the economic base of society has changed, e.g., aristocrats wield social and political power while merchants and bankers wield economic power. The balance of power shifts but there is resistance and conflict, then people exclaim, "How violent!" (I think that that was Trotsky in his The History Of The Russian Revolution.)
(iv) Wells and Anderson imagine a Change inside people whereas Stirling and Dickinson imagine a loss of technology.