Medium reposts Wired's 2008 article about the numbing levels of technical polish used to optimize pop music recordings.
"Playlists of Hot Adult Contemporary stations are determined by a computer, most likely running Google-owned Scott SS32 radio automation suite, which shuffles the playlist of 400 to 500 tracks, inserts ads and idents and tells the DJ when to talk. The playlist is compiled after extensive research. Two or three times a year, a company like L.A.-based Music Research Consultants Inc arrive in town, hire a hotel ballroom or lecture theatre and recruit 50 to 100 people, carefully screened for demographic relevance (they might all be white suburban housewives aged 26–40). They're each given $65 and a perception analyzer—a little black box with one red knob and an LED display. Then, they're played 700 seven-second clips of songs. If they turn the knob up, the song gets played. If they turn it down, it doesn't."