By Paul Robicheau

Despite some hiatuses and a non-lasting change in the guitar slot, X has amazingly soldiered on for four decades since its 1977 formation and 1980-1984 heyday to remain standing with its original lineup.

Exene Cervenka and John Doe of X at Tupelo Music Hall. Photo: Paul Robicheau

A signpost declares “The end is near” in branding for X’s current tour, which the band warns will be their last — like the solid new Smoke & Fiction, billed as the final album that X will make. That’s not an unreasonable expectation given the punk-rock quartet’s age. Despite some hiatuses and a non-lasting change in the guitar slot, X has amazingly soldiered on for four decades since its 1977 formation and 1980-1984 heyday to remain standing with its original lineup.

X isn’t staggering to the finish line either way. The band’s bracing Sunday show at Tupelo Music Hall (allegedly X’s first-ever New Hampshire gig) displayed the group’s versatility, vitality and heart though a tight, engaged 80-minute show. Boston fans hopefully won’t miss Monday’s local follow-up at the Wilbur.

Billy Zoom of X at Tupelo Music Hall. Photo: Paul Robicheau

Of course, tight isn’t a word that readily come to mind in describing the vocal interplay of Exene Cervenka and bassist John Doe. Briefly married in the ’80s, the pair still overlap their contrasting voices –his deep, hers keening — in seemingly haphazard collisions that naturally fall in sync, making them one of rock’s most unique co-singers.

They traded verses before merging for the chorus to the charging new “Sweet Til the Bitter End” (one of four new songs) and harmonized throughout the crashing gait of “Johnny Hit and Run Pauline,” the smoldering “White Girl” and a stream-of-consciousness “I Must Not Think Bad Thoughts” that capped a magical, part-acoustic encore.

The diminutive Cervenka, in embroidered jacket (including the symbols X, 77 and ?) and minidress that pictured dogs playing cards) remained the central wild card. She faded in and out of the spotlight at the mic, an impish enigma crossing and waving her arms, interlocking her fingers and mussing her hair. And she appeared to be having fun in the band’s cover of “Breathless,” playing up her phrases in a moaning Elvis inflection with sighs around the chorus.

Doe served as the band’s musical anchor on bass guitar, dragging one leg to drop into a classic stance and crunching away at his axe in “Your Phone’s Off the Hook, But You’re Not.” It began a three-song run from X’s 1977 debut Los Angeles that menacingly closed with the melodic thump of “Nausea.” And the main set later closed with the group’s feverish cover of the Doors’ “Soul Kitchen,” whose keyboardist Ray Manzarek produced X’s first four albums.

The 1982 album Under the Big Black Sun comprised a surprising five-track chunk of the 23-song set, kicking early with the rat-a-tat “Because I Do” and “Blue Spark,” marked by Billy Zoom’s punctuating slides up his guitar neck. The gently smiling, rockabilly-tinged guitarist now sits as he plays, serving as X’s oldest member at 76, several years past treatments for a second cancer battle (Cervenka, in turn, announced in 2009 that she suffers from Multiple Sclerosis). And Zoom bit into the buzzsaw riff of mid-set climax “The Hungry Wolf,” locking with the pummeled tom beat of drummer DJ Bonebrake (who completes X’s engine room), the guitarist igniting a vibrato hum into a brief, powerful drum solo.

DJ Bonebrake, John Doe, and Exene Cervenka of X at Tupelo Music Hall. Photo: Paul Robicheau

Some encores simply provide more of the same, but X also had a surprise up its sleeves that turned the encore into gold. Doe and Cervenka began with a highlight that wasn’t on the printed setlist, a lovely, rustic duo reading of “If I Were a Carpenter” (as popularized by Johnny Cash and June Carter) to set up a prelude to an equally spellbinding “See How We Are” (the crowd of about 600 cheering as Doe twisted the lyric to reference Revere Beach) and “Come Back to Me” before the band closed with “I Must Not Think Bad Thoughts,” which featured a scintillating vibes solo by Bonebrake while Zoom stood to stick his guitar pick to his forehead and blow away at a mounted tenor sax.

If X sadly never circles around to these parts again, the group couldn’t end on a sweeter note.

Paul Robicheau served more than 20 years as contributing editor for music at the Improper Bostonian in addition to writing and photography for the Boston Globe, Rolling Stone, and many other publications. He was also the founding arts editor of Boston Metro.