Sessions men, erratic jammers, musical wizards, ESP-connected brothers of the road: Marco Benevento and Joe Russo, aka The Duo, really are the hottest thing in Jam Nation. Before the epic residencies in Philadelphia, New York and Boston they had piqued interests and won over legions of converts, but they needed one more boost to thrust them onto the A-list of formidable scene players. Hence, the residencies, with a gigantic national tour to follow.

And what a decision: the residency format, be it "workshop" style or beat-you-til-your-blue saturation of material on an audience night after night, suits the Duo 100 percent. Over three straight Tuesdays in Beantown, they incorporated both formats, mixing up setlists and experimenting in new directions with the same tunes and also adding a myriad of guests.

Watching Marco and Joe in action is hypnotic, and after a while of absorbing their mischievously grinning, challenging interplay, you find your own face plastered with a engaged smile. Apart from the obvious (and quite frankly, insane) musicianship on display at all times, you relax and absorb because you know the two of them are probably having just as much fun as you are, if not more — their grinning theatrics are contagious. The Duo are so intrinsically locked into one another that the rim shots, Wurlitzer bangs, organ lilts and cymbal crashes sound almost like a one-man band at work.

ROUND I
Week one was an exercise in feeling things out and warming the improvisational stove. The Duo’s now-standard "Abduction Pose" opened and the exploration began almost immediately…and went, and went, and went. A superb version full of small touches and big grins that eventually melted into "Impact" and hung about for a bit. The immediate new ingredient evident to this show (and one that would build and build through the three nights in Boston) was the dramatic presence of Marco’s Wurlitzer piano. While it didn’t become a staple until week two, Marco made good use of the Wurlitzer’s rich, near-dirty sound, banging away on the beastly thing in Set 1 and keeping it alive for the comparatively slight Set 2.

The ubiquitous Sam Kininger was the added ingredient in this go round, emerging at the end of Set 1 to rescue a meandering "Darts" and steer it into "Interstellar Space"-Trane territory. He smoked and squawked as the trio landed in "Big Whopper," closing the set with musical aplomb

Overall, round one felt stellar, if a bit too much like a warm-up. Then again, all three Boston shows felt loose and like true "workshops," as if Marco and Joe were able to relax and get playful after the more "high stress" New York gigs with marquee player guests (the "We’re-jamming-with-Warren-fuckin’-Haynes!" look Marco shot off during the Jan. 16 "Misty Mountain Hop" in NYC was priceless). If there was one misfire in week one, it was no collaboration with Josh Roseman’s group, who opened. Their (Roseman’s) set was a fireball, and that Roseman didn’t end up joining the group (or correct me: I had to jet before the evening’s final song) was a forgivable bit of musical blue balls.

ROUND II
Now things really started to cook with gas. In Week II, Marco continued exploring with the Wurlitzer while Joe started to pave different percussive ground with some added kit effects. They opened with a stirring set of originals (hints of "Raindrops" and a few others permeated) before a languid "Mephisto" that didn’t quite find its way. But the Duo are experts at recovering from a flat jam, and the "Darts" that followed was among the highlights of the three week run. Joe was attacking his kit with reckless abandon, playing off Marco’s ideas and coloring them into something cohesive — lots of fun on this one. This heavy set, which had started early and went for nearly two hours (the Duo hadn’t anticipated playing a second this night), finally closed with its one cover, "Myxomatosis" (off of Radiohead’s Hail to the Thief—similar to "Paranoid Android" in composition), a bouncy "Impact" and a meaty "Big Whopper."

Catching their breath, Benevento and Russo returned for a truncated second set that seemed more like an extended encore (four songs, they were obviously exhausted), but brought several guest surprises into the fold. The Slip’s Andrew Barr took over Joe’s kit for the opener (a Monk or Grant Green cover maybe?) that was charming, but Barr seemed content just to keep time with minimal fills, and Joe gave up trying to carry the weight on a shaker and cowbell behind him after a few minutes. Barr is usually a much more expressive drummer — his reticence made Joe’s absence behind the kit feel like a big fat void. Once again, however, the Duo sprang back to life, delivered a ratcheting "High Noon," and then brought up trumpeter Grayson Farmer and guitarist Steve Fell — aka Marco’s cohorts in his Jazz Farmers side project — for some real shredding. "Selma March" was explosive, with Farmer taking the lead on some serious improv and leading the way into an ambient jam (or was it another tune? You never can tell with these guys). These final moments epitomized what the Duo — and the residency format — are all about: experiments, some of which go south, but some of which are absolute knockouts and yield unique moments where all participants top their own games.

ROUND III
Compared to the second night, the third night felt ever so slightly stunted, even a bit rushed. Previous versions of songs like "Abduction Pose" and "Darts" were developed and nuanced; tonight they were quickly explored and then abruptly brought back into their melodic heads. The pace finally chilled out with Radiohead’s "Paranoid Android," perhaps the Duo’s finest cover song other than some of their Zeppelin work (and even the "Myxomatosis" from last week). Marco’s fingers raced up and down the organ keys during the mid-song breakdown, playing a half-swung version of the melody with his right hand and coaxing erratic syncopations with his left, a marvelous amalgam of bending a creative melody into a semi-dissonant harmony. It was downright incendiary next to their able, if sloppy reading of "Smells Like Teen Spirit," which closed the set (The Bad Plus, IMHO, do it far better in a keyboard jazz context).

The second set had serious smoky jazz and chill-bop stylings, paving the way for a second appearance by Farmer and Fell from the week before. Once again, Farmer’s trumpet was the go-to flavor, offering a combination of improv reminiscent of both Miles and KDTU’s Chris Littlefield.

The effect of these residencies, several of which (Boston for sure) will be released on aliveaudio.net, will be huge for Benevento and Russo. They have proven they can hold court for weeks at a time and mix it up, back guests, integrate new elements and overall keep it interesting, often in the same show. The residency ain’t easy, and few groups manage to keep things lively three weeks in a row, especially having to keep up similar residencies in other cities.

As a final aside, even after the Duo had packed up and left for their as-yet biggest national tour following night three, their success left an intriguing byproduct: the continued emergence of the Paradise Lounge.

An ideal place for the small ensemble residency format, the Lounge finally offers the type of cozy, intimate, unassuming sit-and-enjoy place (akin to NYC’s Tribeca Rock Club) that Boston show-goers usually trek to Cambridge to find. With a residency by the Jessica Lurie Ensemble already on the books for April, expect the Lounge to flower into a superb, small show concert stop.