Introspective singer-songwriter Aimee Mann and passionate punk rocker Ted Leo initially seemed an unlikely pairing, and even though their collaboration as the Both has proved to be sweet musical synergy, their putting on a Christmas show was stranger still. But Christmas songs aren't all tinsel and twinkling lights, as Leo explained when introducing "It's a Gift" at Union Transfer on Saturday. "It's largely about sadness and loss," he said, to an approving audience. "Oh, you like that?" he deadpanned. "I guess that's why you're here."

The two-hour revue, featuring a core backing band and a cast of guests, took in the holiday's joys as well as its sorrows, and sometimes set the concept aside altogether. Jonathan Coulton's "2600," about pining for an Atari game console back in the day, was on topic, but "Re: Your Brains," in which a zombie tries to persuade a former coworker to let him in, served as a reminder that craving to feast on human flesh is a constant. Liz Phair's "Ho Ho Ho," was a solid fit, even if lyrics like "That ain't no sleigh bell jingling on the rooftop / The landlord is here and he's changing the locks" weren't brimming with cheer. Nor her hot-to-trot "Supernova," even if, she argued, "It's got a cherub and a star in it."

The evening had moments of outright comedy, as when Mann dressed up as a grizzled, bearded 2015 and Leo a diaper-clad 2016 to duet on "What Are You Doing New Year's Eve?" (Coulton, as an Orthodox rabbi, popped up wearing a sash reading "5776.") And there was welcome sentiment, too: Mann and Phair's "Winter Wonderland" revealed the enduring composition trapped under decades of accumulated schmaltz, like a hardwood floor beneath gaudy shag carpet. Even Ed Ames' kitschy "The Ballad of the Christmas Donkey" was played relatively straight, Leo recalling how it made his otherwise stoic father creep off to weep.

A special kick came from two reworked old songs. Phair's "Why Can't I?" shifted the object of infatuation from a potential lover to holiday decoration, a reminder that, in an age when selling out is no longer a thing, her turn from indie-rock goddess to wannabe pop star produced some of her best music. Best of all was Mann lifting her unofficial ban on playing "Voices Carry," the '80s radio hit from her old band, 'Til Tuesday. True, she rewrote it so it was about a child watching her mom drunkenly stumble in with a new husband, but "This Is Gary" sounded just as sweet as the real thing.