Punk fans tend to select moments in a band’s timeline and freeze them. Having crystallized in the collective fan consciousness what is believed to be the defining moment in the band’s history, they forget the rest.  They may only listen to Danzig-era Misfits, or pre-Generator Bad Religion. After a long career, such as T.S.O.L.’s, even the band itself sometimes does this.

The seminal punk band has been marked by a long and agonizing history of sound evolution leading to fan revolt, bitter legal battles over the name, seismic lineup shifts and death from the late 1970s through the early 2000s.  It was a shape-shifting path that would take the group from being pioneers of the OC hardcore scene to flag-bearers of the new goth-punk subgenre and experimental art-rockers. Through a gradual shedding of its members and an identity crisis, it even spent a moment as a full-on hair metal band in the late ’80s, a period that, by most accounts, is characterized as a brief misstep at best, or a dishonorable discharge from punk at worst. In less than five years, the band went full L.A.-style pop-metal.

But it was the era of the first three releases — the 1979 eponymous EP, 1980’s Dance With Me and 1982’s Weathered Statues EP — that most self-professed punks hold as the most authentic moment of True Sounds of Liberty’s history, and these days that is exactly what the band offers. Sunday night at Billy O’s in Ventura was no exception. Even with three records out since since their reunion in 1999, they are staying true to their roots. Maybe after looking back on the morphography of the last three decades, that’s who the band knew it always was.

Thirty-three years of T.S.O.L. have brought them back here, to a limited capacity, standing-room gig at a bar, probably not unlike those they used to play in the exploding Southern California punk scene in the late ’70s. The band now includes only one non-original member, drummer Jay O’Brien, alongside original members vocalist Jack Grisham, guitarist Ron Emory and bassist Mike Roche. Having played the Santa Monica Civic Auditorium the night before at GV30,  the weekend punk festival featuring basically the Knights of the Round Table of So-Cal punk the Descendents, the Vandals, Social Distortion, Bad Religion, the Adolescents and Black Flag among others) they must still have been buzzing (figuratively — they are all more than 10 years sober) because the mood was electric.

It was everything fans expected and nothing less. While peppered here and there with songs from the post-2000 reunion work, it was otherwise all old-school, from the driving, drumroll pulses of “I’m Tired of Life,” “Sounds of Laughter” and “Dance With Me,” to the melodic and upbeat tracks “She’ll Be Saying” and “Wash Away” from  Beneath the Shadows and the signature punk anthems “Abolish Government / Silent Majority” plus, of course, “Code Blue.” It was perhaps the best $8 I’ve spent  in months.

Grisham wailed and shouted his 30-year-old lyrics as though they were burned into his brain. But none of the confrontational theatrics one might expect from an original punk were on stage Sunday. No wild-eyed, angst-ridden glares that he might have flashed in the Reagan years. Instead, Grisham wore a different expression, a full, plastered-on smile. It was the unmistakable grin of a proud father (he is, after all, a real one to two girls), as though he had personally sired the mayhem circling wildly in front of him, a new generation of punks thrashing furiously to the songs written before half of them were born. A smoke bomb went off. A dozen dudes younger than 30 rushed the stage to sing with Grisham. “Last night we played with Bad Religion and Youth Brigade,” he declared over the elated crowd. “That was fun, but this is way funner.”