Foremost among the things that make it work is Raine keeping her writing intently focused on what the characters are incapable of saying to one another — even those who are physically able to hear. To this end, she tweaks the expected concept a bit. Billy (Russell Harvard, from the film There Will Be Blood) was born deaf but raised in a hearing family that wanted him to fit into their world. The family of his new love interest, Sylvia (Susan Pourfar), is deaf, but she can hear — if only for now, as a genetic defect is gradually robbing her of that ability. Their relationship develops slowly (she has a boyfriend, he's never had a girlfriend), but it picks up a dangerous new momentum once they meet each other's families and see what they've been missing their whole lives.
We never meet Sylvia's parents or siblings, though we see how they, and the others in Sylvia's all-signing circles, impact Billy, who never before understood what an outsider he was. But Billy's family is front and center throughout: His father Christopher (Jeff Perry) and mother Beth (Mare Winningham) are authors; his sister Ruth (Gayle Rankin) and brother Daniel (Will Brill) are back living at home, she because she's making too little money singing opera in pubs and he because he broke up with the girlfriend he'd been living with; and they're all outspoken. It's immediately obvious that these people have spent decades talking over each other, leaving no outsider a definable place — whether Sylvia or even Billy, who was inculcated into their collective (and, to their minds, the larger world) by never being taught how to sign.
It doesn't take long for Billy to want more, and he's willing to go to extravagant lengths to achieve it with Sylvia, who in turn isn't sure she wants to hang on to everything she has. The more able the two are to speak to each other, with either their mouths or their hands, the less they're able to actually say. Two gorgeous keystone scenes underscore this: the dinner in the first act, when a newly signing Billy must translate for the struggling-with-lip-reading Sylvia, and a second-act glimpse inside the bedroom they later share, where they discover how much they're threatening to move past each other as they try to move closer together.
Raine errs occasionally — Ruth is a bit underdeveloped, and forcing Daniel into a near hearing impairment himself as a result of voices in his head is stretching things — but even her mistakes help shore up the underlying theme about the universal importance of acceptance among loved ones. (And no, Billy isn't just a teacher in this regard.) The functional dysfunction of Billy and his family reinforces and amplifies the pressures Billy likely faced in being different, and the many scenes about them all arguing over topics as innocuous as nuts, kimonos, mystery novels, and so on catapult you into the thick of their unique bonds in a way many playwrights would struggle with.
This provides fertile ground for Cromer, who does his typically excellent work here, if operating in a bit lower key than usual. The few flourishes come from the inventive use of Jeff Sugg's projections, which sometimes display surtitles but between scenes rollick with animation of the lyrics to songs that cover set changes. (Scott Pask's lived-in living room set is as tense and cramped as the feelings it contains, and it's starkly lit bit Keith Parham.) The most startling scenes tend to be the most still, with the aforementioned dinner a symphony of subdued stares and clenched attitudes, and the finale so drenched in pain that the characters' explosive inertia threatens to creep into your own bones. But the pace never flags, and the two-hour-plus running time feels, if not quite breezy, then just right.
The same is true of the performers, who emit no fireworks but excite just the same. Harvard makes a firm but delicate transformation from passive boy to active man, letting you see how a determined individual can emerge from a faceless crowd. Undertaking a similar journey in reverse, Pourfar is at least as involving in the way she shrinks Sylvia's worldview to a more manageable pinpoint as her own senses abandon her. Brill bracingly balances Daniel's love for his brother with his own needs, as does Winningham, who crafts a magnetic version of subtle selfishness to contrast with the more overt examples in her brood. Perry is persuasive as the braying patriarch, and Rankin finds an appealing sensitivity (if sometimes too much of it) in Ruth.
But dwelling on any one person is ultimately counterproductive. As its title suggests, Tribes is as much about taking sides as it is finding out who you are, and is thus most memorable when it's at its most crowded and chaotic. The instances — and there are quite a few of them — where the various languages collide with the more threatening force of meaning drive home how difficult it can be to say what you think and feel even when you have a willing audience. One suspects these characters will never be completely comfortable doing that, regardless of the words or tools at their disposal. Raine, however, manages to deliver her own messages about working around these deficits loudly, clearly, and beautifully.