GM Voices is nestled on a rolling, leafy road in Alpharetta, Georgia, an affluent suburb of Atlanta. A recording studio specializing in voice-over work, it produces narration for corporate training videos, voicemail system prompts, and the like — not exactly sexy stuff, but steady, and for the best actors, lucrative. September Day is one such actor, and on a morning in 2011, she arrived to begin work on a special project.

Day, a red-headed, 37-year-old mother of three who’s done work for many high-profile clients — companies like MTV, Dominos Pizza, and Nickelodeon — had been given few details. She knew she’d been hired to do a “text-to-speech” product — something where a computer reads text back in human speech — and she knew that she’d be doing her “early ‘20s” voice (she also has a spunky teen voice she’s used for, among other things, an acne infomercial).