The Milk Carton Kids don’t come on stage with much — two acoustic guitars, a vintage mic, and a conspicuous medicine bag. The whole show, you wonder what tricks they are going to pull out of it.

But there are no tricks to The Milk Carton Kids’ music, and aside from maybe a capo or two, there’s nothing in the bag. For the sensible shoe crowd that they attract, it’s good medicine nonetheless.

The band made good on the tonic that they sell; their songs delivered on the promise of traditional bluegrass with charming flourishes, subtle, reflective songwriting, and an unfettered, unplugged good time. Songs like “Honey, “Honey” and “Girls, Gather ‘Round” highlighted the fast-paced flat-picking expertise of guitarist Kenneth Pattengale, while songs like “Snake Eyes” and “Monterey” offered the slow, reflective, and sometimes dark songwriting that can only come from music that strips itself of excess.

Where The Milk Carton Kids stand out, however, is their lyricism. The duo hits an impressive range of emotional registers with its words. On “Stealing Romance,” a bittersweet waltz, the band flirted with the overture to be “the step in your slow dance” or “the tick-tock in your wrist watch.” But on “Asheville Skies,” The Milk Carton Kids took a brooding turn, lamenting the passage of time that comes from “the heart that beats nocturnal” that “knows not where it goes.”

In a moment that strongly gestured towards Simon and Garfunkel (with whom The Milk Carton Kids are often equated), “The Ash & Clay” gave an understated pacifist message with “We’ll come home before the girls are grown / We’re coming home tonight.”

Notable too was the band’s embrace of irony. The up-tempo, revivalist “Heaven” entreated the audience to stomp, scream, clap, and holler, which the Houston attendees meekly obliged. But in doing so, they unwittingly drowned out the song’s message of disenchantment when they should really have, according to rhythm guitarist Joey Ryan, just shut up and listened.

So too with the song “Charlie,” which at its face is a sentimental tear jerker ballad dedicated to Pattengale’s daughter. After enduring a litany of fatherly cliches — “Charlie, you’ll be strong / Charlie, you’ll be smart / Charlie, you’ll be anything you want to from the start” — we got the big reveal: Charlie doesn’t have a “momma” yet, and therefore doesn’t exist. It’s nice to see someone wink and nod at the levels of hyper-sincerity that at times weigh down the folk genre.

The Milk Carton Kids are well known for their bone-dry banter, which generally involves Ryan performing protracted monologues as an effete, arrogant, tone-deaf man-child. Some of Ryan’s more bombastic moments — referring to child birth as a “violent, dangerous, disgusting medical emergency” that was very traumatic…for him — played for big laughs. But even if that Andy Kaufman-esque character was all an act, after five minutes it wore thin, and after 10 it was exhausting. One wonders if Ryan has worn this face paint a bit too long and can no longer wipe it off so well.

The Milk Carton Kids seem to occupy an interstitial space right now. They’re not quite small enough to play intimate, acoustic venues like the Mucky Duck, but they’re not quite large enough for theaters like the Cullen Performance Hall, which remained dotted with red empty seats throughout the evening. As the folk revival wanes and concert dollars dry up like spilled gasoline, one wonders if the understated harmonies of two men with guitars can still pay the rent. Ryan and Pattengale seem committed to stay leashed to their microphone with their guitars defiantly unplugged. Only time will tell if the market will still be able to bear bands like The Milk Carton Kids, or if audiences will start looking for a new kind of drug.