Anouilh uses the chorus in much the wame way as Sophocles did - though with some twists. As in the classical play, the Chorus comments on the action, gives some background information, and sets the tone of the tragedy. Also, like the classical model, he rarely interacts with the other characters, but gives his observations in soliloquy.
Anouilh's Chorus remains generally neutral, whereas in Greek tragedy, the chorus would frequently take sides in the drama, give advice, and react negatively or positively to the action going on around them. Anouilh's chorus does so only a very little.
Significanly, the Chorus's two long speeches at the beginning include a commentary on the nature of tragedy, and he predicts the fates of the characters. Such was not so in the classical. This has the effect of emphasizing that this is an old tale retold, not something invented for propaganda purposes. It also prepares the audience for the play that is to come; emhasizing that everyone's fate has been dicided, and yet strongly implying that "fate" is a direct result of character.
Like Socrates, Anouilh used the Chorus to make moralistic judgements on the characters' motives and actions. For the audience, the chorus is a guide, leading them through to the action of the play to very specific conclusions the playwright wishes to express. For the characters, the chorus is a conscience, forcing them to examine their innermost thoughts and feelings and to defend their actions. By letting the chourus introduce the characters, Anouilh strengthened their position as guide for the audience, thereby controlling the audience's experience.
When it comes to using the chorus, a director can make many choices. Having the chorus onstage makes a direct conflict between character and conscience. They can "face off", as it were. Using lighting to indicate the chorus is speaking, but keeping the chorus offstage, would give the group a more god-like quality. If on-stage, putting the chorus behind the actors weakens it, but putting it front, or even front and center, adds strength.