Jack Ross, the show's first black character, will be
introduced as part of a storyline about race relations in the time period.
Casting notes sent out to actors' agents this month described Ross as: "Male, 25-30. A musician [singer] at an exclusive club in the 20s. He's black and very handsome. A real man [not a boy] with charm and charisma," The Sun said.
The right actor should "ideally be able to sing brilliantly."
"Overall, he should be a very attractive man with a certain wow factor," the notes said.
Created by writer-producer Julian Fellowes, the award-winning "Downton Abbey" stars Maggie Smith, Penelope Wilton, Michelle Dockery, Brendan Coyle, Jim Carter and Hugh Bonneville. Production on Season 4 is to start March 23.