Flogging Molly’s concert in Bend on Sunday night was proof that I still have plenty to learn about Bend’s music scene.

When the L.A.-based Irish-punk band’s show was announced, it didn’t register much of a blip on my radar. We chose to feature the band on the cover of last week’s GO! Magazine, but thanks to a colleague’s awareness of their popularity here, not mine. Then the show’s promoter told me this could be his biggest event of the year.

I was shocked. I thought Flogging Molly’s revved-up trad-rock show could fill a medium-sized bar, but not the spacious Midtown Ballroom.

Sunday was cold and blustery, as you know, but that didn’t keep people away. By the time I arrived at about 9:30 p.m., the show was already sold out.

The crowd was as big as I’ve seen at the Midtown, packed in tight from the stage to the soundboard and pretty full even from the soundboard back to the bar area. And I think one of Flogging Molly’s secrets is that it appeals to so many different groups of music fan. At this show, mohawks and hoodies stood aside sweater vests and trilby hats; from punks to folks looking for their tin whistle fix, the crowd was nothing if not diverse.

I found a spot above the floor to watch, and commenced with the pre-show entertainment: Watching the pancaked masses jostle for position up front and then, occasionally, help support a crowd-surfer. From my vantage point, it quickly became apparent that there was a weak spot in the crowd-surfing infrastructure — a spot near stage left where at least a half-dozen people plunged suddenly, headfirst to the floor.

I might’ve tried to warn them if they hadn’t all resurfaced with smiles on their faces.

After a short-lived “Flog-ging Mol-ly!” chant, the lights dimmed and a recording of The Who’s “Baba O’Riley” boomed from the loudspeakers. I wondered if the very-pro-beer band chose that song as entrance music for its commentary (“Teenage wasteland. They’re all wasted!”) or simply because it’s one of the most awesome rock songs ever written.

Probably both.

As the song’s Celtic coda kicked into gear, out came a very well-dressed Flogging Molly — all seven of them, led by charismatic frontman Dave King, who picked up an acoustic guitar and launched into a set that would charge ahead at full throttle for nearly two hours.

All for one, one for all

If I didn’t know before why Flogging Molly is such a popular live draw, I do now. The band is as entertaining and unique a hard-rock act as you’ll see. At times, the set verged on metal, with bassist Nathen Maxwell headbanging his way through the heaviest parts and George Schwindt giving the drum set a merciless pounding. Songs such as “Selfish Man” and “If I Ever Leave This World Alive” and “Tobacco Island” were blistering rockers, while “Whistles the Wind” showed off Flogging Molly’s (ever-so-slightly) more mellow side.

Bridget Regan (fiddle, tin whistle) and Matt Hensley (accordion) may be the MVPs of the band, with their instruments adding just the right amount of color (green, of course) to flesh out King’s Irish themes. And King himself is an unparalleled ringleader, marching around stage to engage each band mate during the songs and delivering sharp, witty banter in between. On Sunday alone, he toasted Bendites, redheads, Catholics, the opening bands, Ireland and the Midtown for its non-operational disco ball.

You know a venue is “real” when the disco ball doesn’t work, King said.

The crowd, particularly up front, ate it all up. Fists were pumping and bodies flailing and faces straining throughout the night, and every song that wasn’t brand new inevitably turned into a hundreds-strong singalong.

It’s here, perhaps, where Flogging Molly excels the most — portraying an all-for-one, one-for-all ethos that extends not only to the seven members of the band, but also to all the folks who paid to get in. Maxwell spent as much time saluting the throng and tipping his beer can in its direction as he did playing music. Guitarist Dennis Casey took advantage of a song break to slap every hand he could reach. Banjo player Bob Schmidt hung around after the set talking to fans. King even thanked the security guards and insisted the audience applaud their hard work.

After a raging encore that included the best song of the night — a raucous “Black Friday Rule” — King raised his hands to the sky and applauded the sea of people in the Midtown, and they responded with the loudest cheer I’ve heard in 18 months of attending shows there.

It was clear evidence of the kind of relationship Flogging Molly has with its fans, and vice versa. And it was the kind of exchange that, repeated night in and night out, can propel what seems to be a pretty good Irish-punk bar band to these kind of heights.