When the Drive-by Truckers rolled into the 9:30 Club on July 15, 2006, it was the closest I’ve ever come to actually losing consciousness at a rock show. The gig was beyond sold-out, more vacuum-packed with sweaty bodies than any other supposedly sold-out 9:30 show I can remember. On top of that, the show fell on one of those spongy, airless summer nights that that can make the period between Independence Day and Labor Day in this town feel about six months long.

The Truckers didn’t give a shit, of course. Their 31-song set clocked in at just under three hours. They appeared to quaff just was much Jack Daniels and just as little water as usual. (Maybe they have some band rule about only drinking water offstage, because, you know, they seem like the kind of guys who spend a lot of time worrying about their image.) Jason Ibell, one of DBT’s three world-class singer/songwriter/guitarists, knocked us out with his gorgeous cover of the Rolling Stones’ “Moonlight Mile." Sweat-saturated T-shirts were peeled off. When the Truckers finally let us go, we spilled onto V St. like a gut released from a girdle, gasping and delirious. It was, in other words, a near-perfect evening of rock and roll.

Fast-forward a year to last Friday night. The Truckers return to the 9:30, but they’re not the Truckers they were. Isbell has left, apparently amicably. John Neff has returned to play pedal and lap steel. Legendary keys man Spooner Oldham has joined, for this tour, at least. (He played that instantly recognizable organ part on Percy Sledge’s original recording of “When a Man Loves a Woman,” in addition to playing on hits for Aretha Franklin, Neil Young, Bob Dylan and pretty much everybody else in the Rock and Roll Hall of Fame.) The Truckers are taking stock, road-testing new songs for possible inclusion on their next record, and revisiting their catalogue through acoustic arrangements a la Bruce Springsteen on his Ghost of Tom Joad and Devils and Dust tours. Billed as “The Dirt Underneath,” these shows are meant, says primary DBT frontman Pattersoon Hood in a posting on the band’s website, to ensure the band doesn't curdle into self-parody: “We play very loud and for many good reasons,” Hood writes. “[But] I do sometimes miss how the songs get buried in the process and have always dreaded and feared a day when the whole thing becomes a caricature of itself.”

It sounds like a great idea. The Truckers rock as hard as any band on the circuit, but they also have few equals when it comes to balladry: With Isbell gone, they’re back down to only two of the best singer-songwriter-guitarists around, in founding members Hood and Mike Cooley. Songs like Hood’s “The Living Bubba” or Cooley’s “Daddy’s Cup” — I could give a dozen other examples from each songwriter — have the kind of narrative momentum and incisive characterization that probably isn’t best appreciated at bone-rattling volume in a club. The opportunity to hear these songs performed acoustically, perhaps with some Storytellers-style commentary from their authors, sounds too good to pass up.

At, say, the Birchmere.

But at the 9:30 Friday night, it was clear that a noisy, all-standing club is a lousy venue for this kind of thing. Or maybe it wasn’t the venue at all, but something was off. Hood had explained early on that the band would play an acoustic set, take a break, and then return to “rock [our] fuckin’ balls off.” (He also cited last summer’s 9:30 show as the turning point on a tour that had been fraught with difficulty until that euphoric gig.)

Hood and Cooley alternated lead vocal chores on the eight songs that comprised the show’s slowish first hour. These weren’t fragile acoustic versions — Brad Morgan’s drums and Shonna Tucker’s upright bass lent the performances some heft, and the arrangements were no more delicate than those performed at the 9:30 by, say, Bright Eyes back in March. The crowd wasn’t overtly disrespectful, but the conversations and drink orders you accept in a general-admission environment made it hard for the Truckers’ opening batch of songs — starting with “Heathens” and the revived favorite “Love Like This” — to compete. Three were new, including “Lisa’s Birthday,” the Cooley character study that closed the opening set. Neither man introduced his new songs, however, which added to the difficulty of hearing them for the first time. The crowd received these patiently, and sang gamely along on the oldie “Nine Bullets.” But Hood must have sensed our impatience, because it seemed premature when he announced after only eight songs that the time had come to plug in.

Much as I hate to sound like a fist-pumping philistine who spends ballads in the beer line and lives only to hear the opening riff to “You Shook Me All Night Long,” I have to say this was a good call. When the Truckers returned to the stage and lit into “Puttin’ People on the Moon,” the temperature in the room immediately rose about 15 degrees. This 90-minute “loud” set boasted three more new numbers, including “Checkout Time in Vegas,” a Cooley ballad. But the emphasis was clearly on the barn-burners, with “Lookout Mountain,” “Where the Devil Don’t Stay,” and a half-dozen tunes from the Truckers’ breakthrough 2001 Southern Rock Opera set all earning a rapturous response.

Though he barely spoke to the crowd all night, and sang slightly fewer songs than Hood, Cooley seemed to emerge as the evening’s star. Strumming his guitar as each cigarette burned down perilously close to his fingers, the goateed, lanky singer/songwriter exuded effortless, magnetic cool, providing an anchor for Hood’s more emotive theatrics.

As they had on that steamy night last summer, the Truckers closed the set proper with “Let There be Rock” and opened the encore set with “A World of Hurt.” But then, surprise: A menacing take of Bruce Springsteen’s “State Trooper” from his classic Nebraska LP. Morgan’s antiaircraft-fire drumroll intro to Jim Carroll’s “People Who Died” signaled the close of another riveting, exhausting DBT show. If not as decisive a victory as their last 9:30 appearance, it reassured us that DBT will survive Isbell’s departure without ceding their position atop country-rock food chain, and whetted our appetites for the upcoming record.

I’d still like to see that acoustic show, though. Maybe next time.