As I approached the House of Blues box office across from Fenway Park to grab my press pass for Saturday’s Mountain Goats concert, a group of baseball fans leaving the Red Sox game asked who was performing. When I told them, one seemingly boozed-up guy who had clearly never heard of the band mocked their name and feigned excitement. But another passerby said, “Wait, The Mountain Goats are playing? Love that new song…” and he nearly wound up joining us.

So the Mountain Goats, either you love ’em… or you never heard of them (or like Mrs. Swellesley, you’ve heard plenty of singer John Darnielle’s unique and reedy voice, and you ask your husband to prep for the concert using headphones).

The Durham, N.C.-by-way-of-Claremont, Calif. band has been around in one form or another since the early 1990s, attracting an indie folk-rock following with their often obtuse, though memorable lyrics that include references to everything from St. Joseph baby aspirin to a monkey in the basement. Among the curious titles on the Boston set list: “Cadaver Sniffing Dog,” “Getting into Knives,” and “Liza Forever Minnelli.”

With the band’s longevity, you might expect an older crowd to have filled the 2,200-person capacity venue, and while that demographic made a strong showing, the Mountain Goats also now pull in the TikTok generation thanks to their 2002 divorce anthem “No Children” going viral on that social platform in 2021. Fans across the spectrum clapped and bobbed along to some songs, and of course shook their heads and pointed their “bony fingers” during a rousing edition of “Up the Wolves.”

Given that singer/guitarist/pianist/author John Darnielle has written hundreds of songs under the Mountain Goats moniker, the band can take its set lists in any direction, and on its current tour it’s generally making the youngsters and the rest of its fans wait ’til the end for “No Children” and some of their other songs that have become sing-alongs. The Mountain Goats chose in Boston to take the slow burn approach to its set list, with a few of their livelier songs mixed in early among slower (their opener, “The Slow Parts on Death Metal Albums,” literally includes the word “Slow” in the title) and more obscure ones. They then pounded out crowd-pleasers over the last 45 minutes or so of the roughly 2-hour show, with Darnielle dramatically shaking his head in anger for certain lyrics and pogo-ing at other times, while bassist Peter Hughes increasingly chimed in on vocals.

The rhythm section of Jon Wurster on drums and bassist Hughes set the mood on lower-key pieces such as “Younger.” Straightforward lighting in reds, purples, greens, and yellows added ambiance. As some in the crowd grew restless during Darnielle’s 3-song solo set (one heckler encouraged Darnielle to move onto the next song on the set list), it also perhaps took inspiration from the upcoming “This Year,” to paraphrase its lyrics: “I’m going to make it through this ~~year~~ solo set if it kills me.”

The 4-piece band (singer/guitarist/pianist, keyboards/brass, bass, and drums) on this night sometimes added a fifth in the person of Kyle Leonard, a recent local high school grad who wowed on the sax and quickly became of fan favorite of the cheeky crowd, which broke into “Kyle! Kyle!” chants throughout the show. Darnielle quipped regret at not making Kyle t-shirts. While not all Mountain Goats songs feature the sax, the instrument adds punch to numbers such as “Cry for Judas” and “The Diaz Brothers” both on recordings and live. Leonard and Mountain Goat member Matt Douglas doubled up on the brass for those songs. They respectively worked the baritone and tenor sax on “Foreign Object,” a choice from the band’s pro wrestling-themed 2015 album “Beat the Champ” that features the jauntiest chorus about jabbing someone in the eye that you’ll ever hear.

Darnielle and Douglas also joined forces on guitar on rowdier songs, though you had to cross the street to the MGM Music Hall if you wanted truly soaring guitar solos: Carlos Santana was playing there. Drummer Wurster, formerly with the band Superchunk, punctuated songs like “You or Your Memory,” which felt much bolder live than on recordings.

One highlight of the show was the performance of “Clean Slate” from the band’s upcoming “rock opera” album dubbed “Jenny from Thebes,” with Darnielle switching over from acoustic guitar to keyboards. This was only the second public playing of the song, which the night before had debuted in New York at the Rooftop at Pier 17, a scenic and roomy venue I’d taken in last month and highly recommend if you’re in the big city. While crowds can cringe over too much new material at shows, “Clean Slate” seems like an instant classic for Mountain Goats fans with its ominous chorus of “Remember at your peril, forget the ones you can.” It starts with tinkly piano and transforms with flourishes and hooks that would make Belle & Sebastian proud. Darnielle shook his head after playing the song, commenting on the enthusiasm of Mountain Goats fans: “That’s a brand new F-ing song and half the people in here know it already.” The album’s due out Oct. 27.

Darnielle started the show modestly by announcing, “Hi, we’re the Mountain Goats,” then had a playful rapport going with the crowd throughout the show, acknowledging his Chicago Cubs support (“I know how you feel”), puzzling over ovations for him hydrating, and dropping local references, even switching in Somerville for Austin in the song “Source Decay.”

The Mountain Goat GOAT introduced “First Blood,” which references John Rambo and Sheriff Buford Pusser, as a dance song. When it came to previewing the song we’d all been waiting for, “No Children,” Darnielle introed the bitter divorce song sung by the band with big smiles and accompanied/overwhelmed by the crowd’s participation, as being “for the lovers…who have lost their way.”

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