One of the biggest differences between the chorus in Sophocles' Antigone and Anouilh's is that in Anouilh's the chorus serves as more of a narrator while in Sophocles', customary of Greek tragedies, the chorus functions as more of a character.
Anouilh's chorus is seen the most in the opening of the play in which it serves as narrator by introducing all of the characters. It even gives background information related to the characters that is neither found nor alluded to in Sophocles'. For example, when the chorus introduces Haemon, it characterizes him as one who would be more apt to fall in love with Ismene than Antigone, which is absolutely not in Sophocles' version. The chorus even tells a tale of Haemon dancing all night with Ismene but then going in search of Antigone, finding her all alone and, apparently, being so taken by her lost and needy nature that he asks Antigone to marry him, as we see in the lines:
... suddenly he went in search of Antigone, found her sitting alone--like that, with her arms clasped round her knees--and asks her to marry him. (p. 4)
In the same way that the chorus delivers background information surrounding Haemon, the chorus also relays other character background information invented by Anouilh, making the chorus function as more of a narrator.
In Sophocles' Antigone, the chorus also does some narrating, but not nearly as much. For instance, the chorus relays the background surrounding the moment that the two brothers killed each other and what led to it. However, for the most part, unlike Anioulh's, the chorus functions as more of a character. The chorus represents the elderly, respected citizens of Thebes and, as a character, frequently interacts with Creon. Not only that, the interactions serve the function of underscoring the play's morals. For example, the chorus advises Creon to listen to Haemon when he protests Antigone's sentence, saying that he is speaking wisely, as we see in its lines, "My lord, if someone speaks in season, you should learn, and you also, for both sides have spoken well" (736-737). At the end of the play, the chorus is also responsible for advising Creon to listen to good counsel and to release Antigone, thereby showing us just how much the chorus is both responsible for underscoring morals and for acting as a character by interacting and even guiding Creon.