One of the things that strikes me about this chapter is how, like the many others in this play-acting section, it works through contrast. The structure is based on antithesis. The analogy might be the kinds of analysis the heroic couplet lends itself to, which also often contains an antithesis within an antithesis.
First, the couples. I think we have our first hint of a coming unexpected connection between Henry and Fanny. Soon after the chapter opens we are told how Fanny is drawn again and again to watch Henry and Maria act; how it was a great "pleasure" for her to go and see his acting especially: "She did not like him as a man, but she must admit him to be the best actor." (Maria, she sees, is not acting at all.) I suggest this scene looks forward to Henry's reading aloud from Henry VIII which so irresistibly absorbs Fanny once again (Mansfield Park, Chapman I:18, 165). I wouldn't make too much of this, but at the close of the chapter, it is Henry's words which the narrator quotes as entreating Fanny: "'You have only to read the part'" (172).
We are not permitted at any time to see that indefatible pair, Maria and Henry. This is deliberate, Austen does not want us to be drawn in--it is not to her purpose to have us sympathize either with Maria or be allured by Henry). But we are with Fanny when she watches Mary and Edmund "play-act." Of course Mary and Edmund's play-acting is implicitly contrasted with Henry and Maria's; the former is a form of courtship, for they could marry; the latter seems to be a substitution for a real relationship (or at least Henry would like to think it is).
Again Fanny is the intensely absorbed observer. Looking forward to the close of the chapter, Fanny need only "read" with Mary and then prompt for Edmund and Mary, but she is "so agitated" she turns "away exactly as [Edmund] wanted help. Fanny at least thinks she is seeing two people really making love or courting, and those who would deny that Edmund loved Mary have to ignore the narrator's downright comments that Edmund and Mary know "great" "joy and animation" in finding themselves together, that they speak with '"great warmth," that their "spirits" "glow," that as Edmund as Anhalt proceeds with his proposal of marriage through an idealistic description of affectionate marriage to Mary-Amelia, his "spirit" "increases" to the point where, as suggested above, Fanny must turn away because what is in front of her is too clear. The narrator tells us Fanny feared she had made a "very suffering exhibition of herself," but we know that they haven't been paying any attention to her at all; as the narrator comments, "she deserved their pity, more than she hoped they would ever surmise" (170).
Another contrast or antithesis in the chapter is that is set up between Fanny and Mrs Norris. Fanny is the sympathetic courteous listener, the one to whom everyone brings their complaints (she recalls Anne Elliot strongly here); she is also, curiously, linked repeatedly with Rushworth. It is she who out of "pity" tries to teach hm, to give "him all the helps in her power, trying to make an artificial memory for him." Fanny is intently aware of Rushworth; we are told it is Fanny who "avoids the sight of Rushworth" when Henry again proposes rehearsing with Maria (168). It is in Rushworth's pink satin cloak (now there's a visual joke) that Mrs Norris once again seizes an opportunity to harrass and insult Fanny as never doing anything. Fanny takes "the work quietly without attempting any defence" (166-7).
Here I think she stands in for Maria in a way, and so we get an antithesis within an antithesis. Fanny's behavior is also the very opposite of Maria's. Maria has been the most petted girl; Fanny the most demeaned and insulted. It is Maria who Henry seduces and plays game with (because she will play back); it is Fanny she whom Henry will fall in love with. Maria marries sheerly for money (and spite); Fanny will not marry without affection. Maria disdains and ignores Rushworth; Henry sees it in her eyes from the beginning; it is Fanny who is driven to help Rushworth (because she is too good-natured not to), she whom he turns to with a "black look" to confide the return of his jealousy (165). The analogy and antithesis is kept up quietly in this chapter but it's there.
One might remark that it seems to be only Fanny who realizes how deep the well of emotion into which Maria has been drawn. We are told not only is she "useful" to all, and as much "at peace as any" (very little), but she observes the others in ways they cannot. Her lack of ego allows her to see beyond her. Another interesting antithesis here is that Maria is given no presence; there's no sense of her except through Fanny's mind; everything we see here is either filtered through or affected by Fanny's consciousness.
Mrs Norris's malice towards Fanny is the main contrast. She is totally selfish, unaware of anyone but herself except if she feels threatened by them or can control or feel herself more powerful through them. Maria does repeat this selfishness, through she shows she had passions Mrs Norris cannot imagine. One cannot imagine by the way Mrs Norris reading a book, much less acting or emoting for real or selflessly from the wings prompting another.
One striking thing about Mrs Norris's continual menacing of Fanny though (and it's played upon in this chapter too), is her spite is so superfluous and her nasty comments very often in the immediate sense motiveless--Fanny does nothing to provoke the woman. I suppose we might say this contrasts with the rest of her behavior which is greedy, grasping, and continually a reflection of her ego and drive for power and love of manipulation. For example, she says with nothing to gain that I can see, that Fanny is "not one of those who can talk and work at the same time" (167). This is precisely perverse. Fanny is the cleverest one in the room; as Mary hints, she's got the play memorized. It is said in response to Lady Bertram who defends Fanny on the score of Fanny's delight with the play-acting. Those of us who have noted what Lady Bertram sees she sees aright, might note this one. We might note here that Lady Bertram does show some interest in what "the play is about;" all Mrs Norris can think about is creating green festoons which she will steal away. (I find her attacking Jackson's son for "sponging"-- Maria's word--one of those many apt sardonic jokes which are scattered throughout this novel.)
Or perhaps we should understand Mrs Norris's malice as part of the fairy tale element of the book. Mrs Norris is the nightmare witch who is nonetheless not overdone so that the reader can identify her with the obtuse densely selfish tenacious presences she (or he) has had to endure--and Fanny, well's she's Cinderella who will turn into a princess, again realized in a realistic psychologized art.
A final contrast is of course the intense climax of it all. Everyone seems so animated; they seem so emotional about everything: Yates "storming away in the dining room;" even Tom at one point "in despair" because Mrs Grant is kept away by Mr Grant's bad digestion (169, 171). This is the strongest emotion he ever shows in the book. And then when they are about it, deeply absorbed as they think, in bursts Julia with the "My father is come! He is in the hall at this moment" (172).
It's curious how one feels the silence on the page. It seems to leap out at one. It's as if they have been playing at petty things, and now reality in the form of Sir Thomas has come. We learn that Mrs Norris's instintive first gesture was to hide that satin cloak. There is another slightly askew antithesis here: it exists in the misunderstanding that awe contains. Mary thinks ah, if only Sir Thomas could see, he would "bless himself" (169) and we are led to feel that the opposite is true, that Sir Thomas is all density, sternness, sobriety. In fact the man who turns up has a "voice quick from the agitation of joy;" he is exhausted, "burnt, fagged, worn," filled with "tender feeling for his family, wanting only to get along and have no further contentions (he's had enough in Antigua), and all fondness for the girl who is most loathe to go into the room, for "my little Fanny." He is filled with far more intense and authentic emotion than any of them. He has a depth, is endowed with a weight of presence and remarkably real voice too.