Claire Elise Boucher hates all her names, especially her middle name, but even the name she invented a decade ago, the name she performs music under and is famous as: Grimes. “I think I’ll kill ‘Grimes’ soon,” she says. “It will be a public execution followed by—by something else. I shouldn’t say yet.” Meanwhile, for now, she asks to be called c (italicized and lowercase). Just like, as she’s fond of pointing out, the shorthand for the speed of light in a vacuum, or 186,282 miles per second.

“ ‘Claire,’ ” c says, “is done...