With Dropkick Murphys at full roar, it must be that time of year again

Dropkick Murphys frontman Ken Casey leans into the crowd at MGM Music Hall at Fenway Saturday night.Ben Stas for The Boston Globe/The Boston Globe

Are our Dropkick Murphys in danger of becoming — shudder — a mere band? Time was, their annual St. Patrick’s Day concert extravaganza was an amiably chaotic, anything-goes affair that seemed like it could tip over into a riot at the drop of a scally cap, hosted by a throng of toughs who looked like they’d knock you to the ground for looking at them wrong and then buy you a drink after. Can a Murphys show that isn’t overrun by a stage full of spirited fans swaying unsteadily to “Kiss Me I’m [Extremely Drunk]” be said to be a Murphys show at all? Where once the band looked like a street gang, on Saturday it looked like a band.

Of course, that band is plenty ferocious purely on its own, and at the MGM Music Hall at Fenway on the third night of a sold-out four-night run (including a final show at House of Blues), every song was a fist, whether it was held up to the sky, their hearts, or someone’s face. The three-guitar attack was scarcely diminished when one or more was traded for accordion or mandolin; it simply changed the tone of the band’s roar, not the power. “As One” was just as heavy as the gleeful warning of “The Boys are Back” despite having an Irish whistle as its lead instrument, banjo rolls led into the charge of “The State of Massachusetts,” and “Ten Times More” was huge despite being nothing more than a military tattoo on drums and harmonica as Ken Casey declaimed at full fervor.

Dropkick Murphys perform Saturday at MGM Music Hall at Fenway, the third of the band's four sold-out shows in Boston.Ben Stas for The Boston Globe/The Boston Globe

Despite Casey’s raspy yip possessing an inarguable authority that helped compensate for the absence of vocalist Al Barr (on leave from the Murphys for family reasons), a great many songs sounded incomplete with just one singer, calling out for half a dozen more, if not hundreds. It was easy to get the impression that if Casey suddenly lost his voice, the crowd was prepared to fill in for him on a moment’s notice without missing a word.

That unity, that loyalty — in both directions — between audience and band remained in full force. With “Fields of Athenry,” “Queen of Suffolk County,” and others telling stories of imperfect folks who merit second chances (if not first ones), the Murphys kept the big, beating heart at the core of the band on display for anyone willing to share their own. Their empathy still hit like a punch.

Pro-union, pro-worker, and pro-brotherhood, Quincy’s Jesse Ahern opened in acoustic-troubadour mode, offering a gravel-throated humanism that recalled both the Dropkick Murphys and the Clash. The airy, easy joy of the Turnpike Troubadours followed, a country band minus country trappings who in the context of a Murphys show had the implied Irishness of the genre teased out and pulled gently to the fore.

DROPKICK MURPHYS

With the Turnpike Troubadours and Jesse Ahern. At MGM Music Hall at Fenway, Saturday.