The comic relief is perfectly real

Exactly. And this production's glorious nonsense is an ingeniously effective antidote to reality, not just for the narrator but for all the rest of us struggling mortals.

Ably directed and choreographed by David Connolly, with a crackerjack cast that plays each preposterous scene to the hilt, the exhilarating SpeakEasy Stage Company production of “The Drowsy Chaperone’’ is all but guaranteed to banish your blues.

The witty songs by Lisa Lambert and Greg Morrison, as well as the clever book by Bob Martin and Don McKellar, are cunningly structured for the Age of Irony. The creators of “Chaperone,’’ which won five Tony awards in 2006, give a contemporary audience license to roll our eyes at the hokey conventions of old-time musicals — Those ludicrous, wafer-thin plots! Those implausible romantic pairings! — while also tapping into our semi-secret nostalgia for the frivolous enjoyment delivered by the tuneful confections of yore.

“When a character is in crisis they sing and they dance,’’ the narrator observes. “Which is so much more interesting than just whining about it.’’ Amen.

The narrator, called simply Man in Chair and played superbly by Will McGarrahan, lives in a drab apartment adorned with photos of vintage stars (Astaire, Harlow, Hepburn, Garland) who possessed a quality that seems singularly lacking in his life: glamour.

Ah, but once he cues up a recording of his favorite Broadway musical, a 1928 trifle called “The Drowsy Chaperone,’’ his apartment suddenly opens up to reveal a lavishly painted backdrop (vividly designed by set designer Jenna McFarland Lord) in front of which that very production has come to life. As the story unfolds, he periodically freezes the action to offer commentary, both sardonic and affectionate, and to tell us the back story of the stars.

It is the wedding day for sexy star Janet Van De Graaff (McCaela Donovan) and her vapid swain, Robert Martin (David Christensen). Donovan is vibrantly funny, especially in “Show Off,’’ a number where Janet pretends to renounce the spotlight while reveling in it more than ever. Christensen is hilarious as the self-infatuated Robert, whether singing “Cold Feets’’ to a mirror and tap-dancing with his best man, George (Brian Swasey), or with Donovan in a duet on “Accident Waiting to Happen’’ while blindfolded and on roller skates.

Since it’s considered bad luck for the groom to see the bride on their wedding day, Janet’s chaperone (Karen MacDonald) is assigned the momentous task of keeping her out of Robert’s sight. The problem is that this chaperone is not just drowsy but perpetually tipsy, thanks to the Prohibition-be-damned flask of hooch she keeps in her cleavage. In a show-stopping performance of “As We Stumble Along,’’ MacDonald memorably captures the chaperone’s mixture of world-weariness and go-for-the-gusto abandon.

The marriage is to take place at the home of Mrs. Tottendale (Kerry A. Dowling), a dotty grande dame. Her butler, helpfully named Underling (Robert Saoud), has to keep reminding her of the scheduled nuptials and also point out, during “Love Is Always Lovely,’’ that she has gotten a few things wrong about classic love stories. (“Romeo and Juliet’’ did not, as she believes, end happily).

Janet’s plans to give up showbiz and leave Feldzeig’s Follies spell trouble for Feldzeig (J.T. Turner), the producer. He is coping with an ambitious, bubble-headed chorine, Kitty (an amusing Sarah Drake), who wants to fill Janet’s shoes, and, more pressingly, with threats from two gangsters disguised as pastry chefs (Ryan Halsaver and Joe Longthorne) who remind the producer that his show’s biggest investor is their mob kingpin boss. So Feldzeig tries to prevent the marriage by enlisting a self-styled Latin lothario named Aldolpho (Thomas Derrah) to seduce the bride-to-be.

Played by Derrah in deliciously over-the-top style, Aldolpho is only too happy to oblige, but he mistakes the chaperone for the bride. This sets up what, to many Boston playgoers (including this one), is a working definition of theatrical nirvana: Derrah and MacDonald performing a duet. A seduction number called “Aldolpho,’’ it’s a riot of comic invention by two of the best actors around.

Moments like that remind us how elusive, how fragile, and how necessary is the hard-to-bottle magic of shows like “The Drowsy Chaperone.’’ When a character is lifted up by the cast at the end, we know exactly how he feels.

It’s not real. It’s a musical. And thank heaven for that.

Don Aucoin can be reached at aucoin@globe.com.