The General Motors Assembly Plant in Arlington is filled with cacophonous sounds. Whooshing and whirring hydraulic robot arms slice through the air with efficient grace. A conveyor system more than 28 miles long transports disemboweled SUV bodies with a rhythmic clank-clank-clank. And everywhere there is music — distinct bell tones that sound like a child picking out a melody on an electric keyboard. The notes are familiar: the Star Wars theme; “Mary Had a Little Lamb”; “Twinkle, Twinkle, Little Star.” Each song snippet denotes a specific workstation that needs help or more parts in this vast, meandering place — 4.25 million square feet on 250 acres. Touring the sprawling assembly line, I make a joke about the famous five-note motif heard in Close Encounters of the Third Kind. Turns out, they have that, too.