Though the celebrations came last night (complete with cake and champagne), it was actually one year ago today that the Bohemian Caverns Jazz Orchestra made its first appearance on the stage of the U Street club whose name it bears. “This group is something special,” I wrote at the time. “If the orchestra can maintain the level of energy and commitment it provided in its debut…then it will be a band to watch.” I also suggested that the Monday-night slot was a potential tough sell for the band.

How right, and wrong, I was! On its birthday, the BCJO has lost none of the energy and commitment it showed in those heady days of April 2010. On the contrary, the 17-piece band’s enthusiasm shines even brighter now than it did then. They are a little more seasoned and cohesive, having had time to learn each other’s strengths and styles. And they all sound like they love the hell out of what they’re doing. That’s perhaps why the Monday concern has not been a concern at all: The band regularly sells every seat in the house.

A lot has changed in that year of life—-in fact, a lot had changed in its first six months of life, including some personnel changes and the expansion of the trombone section. Today things are even more different, especially among the trombones. One of that section’s members, Ryan McGeorge, actually doesn’t play the standard slide trombone at all, but euphonium and valve trombone. McGeorge and Darius Jones succeed former trombonists Corey Wallace and Greg Boyer—-the latter being among the most powerhouse musicians ever to grace the Caverns’ bandstand. In his absence, however, a newfound balance of power exists within the section, a good thing for the instrument that more often than not anchors the arrangements.

That’s not to say they’re not distinct players, though. Shannon Gunn has an unusual heft, playing short phrases where the pauses in between feel even mightier than the phrases themselves, and lead player Steve “Nature Boy” Shaw plays glowing, fluid lines in pieces like “Lady Bird” and “Blue Cellophane.”

In the trumpet section, only one original member—-BCJO co-director Joe Herrera—-remains. His current cohorts include Brad Clements (not available last night), Mike “Bags” Davis, and D.C. favorite Donvonte McCoy. Here, too, there’s a peculiar balance in their sounds: Davis has the brightest tone, McCoy the darkest, and Herrera works in between. There also seems to be a new adventurousness tothe section, perhaps because of McCoy’s sublime lyricism (heard in a brilliant solo on Thad Jones‘ “From One to Another”).

The rhythm section and reeds remain intact from the first night (though last night there were substitutes in both: alto saxophonist John Kocur, nicknamed “The Smoker” for his extraordinary technique, sat in for absent Brent Birckhead, and dynamite drummer Lydia Lewis for Dave MacDonald). There’s a lot of power in the reeds, with ’50s-ish blowing-session muscle in tenors Charles Phaneuf and Elijah Balbed and cream in Sarah Hughes‘ alto; still, it’s likely the rhythm section that gives the BCJO its special flavor. Specifically, it’s pianist Amy Bormet, as crucial to this band’s sound as Johnny Hodges was to Duke Ellington’s. Bassist Regan Brough and guitarist Rodney Richardson are terrific players who bring incredible things to the table, but without Bormet, the band would have to seriously alter its direction.

Its direction, by the way, still sparkles, with classic tunes and arrangements associated with Ellington, Jones, Gil Evans (“Yardbird Suite”), and Maria Schneider (“Lady Bird”), among many others. A particular highlight of last night was a driving take on John Lewis’ arrangement of the classic “Move.” But the musicians themselves also contribute to the book; Bormet provided the sumptuous, loose waltz “Lightning,” another highlight with its gorgeous flugelhorn line from Herrera. It makes for an additional layer of ambition for the orchestra: to find new depth and perception in the work of the big-band titans is one thing; to find new depth and perception in itself is quite another.

One year into its life, then, the BCJO finds itself not only fulfilling the promise it set out with at birth, but heading in equally promising new directions and doing so with aplomb. They’re an essential force for D.C. jazz, and they’re coming along spectacularly. This writer left the club with one overriding impression: That I’ve got to go out and see them more often.