A year ago, the producers of “The Color Purple,” the Broadway musical adapted from the Alice Walker novel, called the singer and actress Jennifer Hudson and asked if she would consider joining the cast of the show’s revival. Ms. Hudson did not hesitate.

“I said: ‘Sure. Yes. Great. Got it. Yup,’” she recalled.

Only then did she wonder which role they wanted her to play.

The answer: Shug Avery, a voluptuous nightclub singer who awakens the musical’s heroine, Celie, to love and sexual pleasure.

This was something of a surprise.

Ms. Hudson knew the musical well. She had seen earlier productions twice in New York and twice in Chicago. She listened to the cast album often. “But I had never imagined myself as Shug,” she said. She thinks of herself as “the big girl with the big voice and the big personality.” Not a siren. Not a “Queen Honeybee.” Not a woman whom the novel describes as “so stylish it like the trees all round the house draw themself up tall for a better look.”