Arianne Phillips, the Academy Award-nominated costume designer, spent years unpicking layers of truth and fiction to create the wardrobe for Bob Dylan’s character in the new biopic “A Complete Unknown.” The movie, starring Timothée Chalamet, focuses on the origins, and motivation, of the famously enigmatic singer-songwriter. Phillips says coming up with the costumes wasn’t easy, and there was a lot of guesswork involved. “Our story is about Bob’s origin — finding his way to New York City in search of his hero, Woody Guthrie and his relationship to fame. A biopic on him is quite tricky because he is a very cryptic person, who has kept a lot of myths alive about his life. He’s never been really forthcoming and it’s part of his persona — he’s this mythological character that he’s created for himself,” says Phillips, who worked closely with the director James Mangold. A costume sketch for “A Complete Unknown.” Phillips says she managed to create a screen persona by shining a light on Dylan...