You know that something small but demographically significant has happened when an off-Loop ensemble puts away the pretense of eternal youth and stages a chestnut like I Do! I Do! Based on Jan de Hartog’s 1951 comedy The Four Poster (one of those scripts that, like La Ronde, seems to inspire loads of adaptations but very few actual productions), this musical by Fantasticks creators Harvey Schmidt and Tom Jones ran on Broadway for a year and a half in the mid-60s and now seems most attractive to the sort of audience that glows with the soft iridescence of blue rinse. Director Michael Weber’s version for the American Theater Company updates the chronology and technology of the original, but it remains a show of mostly saccharine charms aimed squarely at alter cockers.

And possibly alter cocker wannabes. I Do! I Do! appeals primarily to idealized feelings of nostalgia, which I suppose can include nostalgia for things one hasn’t experienced–and given current statistics, probably won’t–like a long and more or less happy marriage. The show as revised by Weber follows its two characters, Michael and Agnes, from their wedding night in 1957 (the original starts in 1895) to the day in 2007 when they move out of the Chicago house where they’ve raised their two kids, launched Michael’s successful writing career, and suffered their midlife crises.

All along the way, naturally, they sing–about their awkwardness as two virgins negotiating their first intimacy (talk about idealized nostalgia), and about the pregnancies that will make further intimacies temporarily all but impossible. About Michael’s self-centered focus on his career and the extramarital fling that will get him banished to the couch while Agnes considers grabbing her share of the sexual revolution. About their shared dream of freedom once the kids have left, and Agnes’s empty-nest trauma when they do. Their marriage–and therefore the show–moves like a pendulum: swinging outward over and over again into crisis, returning in smaller and smaller arcs until Agnes and Michael finally come to rest dead center, together. The show’s signature song, “My Cup Runneth Over [With Love],” punctuates and celebrates their periodic returns to equilibrium.

If you’ve been married for any length of time, the deja vu here can be vivid. If you’re also a Chicagoan and a member of the boomer generation, it can get a little uncanny. With the help of projections by designer Mike Tutaj, Weber uses old film footage of Chicago and its icons to establish period as Michael and Agnes age. Some of that footage seems to stretch back to the 30s (when, we’re told, Michael and Agnes were born), but other clips depict such boomer landmarks as the WGN kids’ show Garfield Goose and Friends. Identifying with the characters’ marital issues while simultaneously getting thrown back to kindergarten was the proverbial mindfuck: my life flashed before my eyes on multiple tracks, momentarily collapsing my marriage into my parents’ marriage–and, I guess, turning me into my own son.

The odd slip down a Freudian rabbit hole aside, there’s not much depth to the depiction of marriage in I Do! I Do! Resolutely upbeat, Schmidt and Jones stick to the major chords, resisting whatever temptation they may have had to go poking around in potentially dark variations. Even Michael’s infidelity is forgiven with little sturm and even less drang, as if Agnes found it fundamentally acceptable–though nothing we’ve seen of her up to that point suggests such a free-spirited attitude. The show gets one profound truth absolutely right, however, which is that the secret of a long marriage has nothing at all to do with resolving conflicts between you and your mate. Rather, it’s entirely about accepting them. Nothing gets fixed in Agnes and Michael’s marriage, as nothing ever really gets fixed in anybody’s marriage. Staying together at first because they don’t want to be apart, they end up staying together because they can’t conceive of being apart. And that’s love.

Actors Heidi Kettenring and Stef Tovar have chances to up the emotional stakes between Agnes and Michael but don’t take them. Kettenring in particular seems reluctant to get seriously ugly with Agnes, despite lines that suggest a sarcastic, frustrated streak in the character. She’s much more at home with goofy/endearing, and she’s good at it too–so it comes as a complete surprise when Michael accuses Agnes of having been cold toward him. Of course, he’s attempting to justify his affair at that point, so the charge may reasonably be taken with a grain of salt.

Whatever her omissions, Kettenring sings and moves well and makes plenty of good use of her animated comedienne’s face; she’s fun to watch if overly fond of shtick. With his limited singing range and stocky body, Tovar is nobody’s idea of a romantic lead. Still, he provides a Michael who’s charming without the saccharin and gives the production some welcome idiosyncrasy. Between them, Kettenring and Tovar never manage to fix I Do! I Do! any more than Agnes and Michael fix their relationship–but they do keep it going. v

Through 11/11: Thu-Fri 8 PM, Sat 4 PM and 8 PM, Sun 3 PM, American Theater Company, 1909 W. Byron, 773-929-1031, $30-$35

Art accompanying story in printed newspaper (not available in this archive): I Do! I Do! photo by Johnny Knight.