The details practically write themselves into a Billy Joel song: The gray-haired guitarist with a philosophical bent and the dimly lit pub where he’s been playing since 1985. The beleaguered Hill staffers half-listening as they dull the pain of budget negotiations with a post-work drink. The regular at the end of the bar, sipping Guinness and wondering what this place will feel like after Pete Papageorge ends his long-standing gig here Saturday.

“Things move along, I guess,” Tony Dowling says from his perch at the bar.

That’s the chorus.

Papageorge, the man crooning folk tunes from a platform by the bar at Kelly’s Irish Times, first sat in that spot nearly three decades ago. Outside, Ronald Reagan was in the White House and Marion Barry was the mayor. Nearby Union Station, which had reportedly featured cigarette burns on its carpets and toadstools growing in its corners, was closed for refurbishment.

Inside, Papageorge played “Sweet Caroline” and “Take Me Home, Country Roads” to soppy Friday night crowds — they’d sing along, enthused and off-key.

Pete Papageorge performs for an audience of now far-flung Catholic University alumni, who set up a reunion to see one of his last performances at Kelly’s Irish Times. (J. Lawler Duggan/For The Washington Post)

The week before Papageorge’s last show, the Irish Times’ red doors shut out a chilly winter night and a changed city. Union Station gleams, just-built condos line North Capitol Street. The newly swankified neighborhood a few blocks north has acquired an appropriately swanky new nickname: “NoMa.”

Inside, Papageorge still plays “Sweet Caroline.” The crowds still sing along.

“It’s funny, people want the same old stuff,” Papageorge says. “It’s the temper of the times, perhaps. What’s going on in the world. They want something that doesn’t change.”

Until this split, which Papageorge describes as amicable but not his choice, the Irish Times has mostly complied with that wish. As far as the pub’s staff is aware, theirs is the longest-running bar-musician relationship in Washington. Papageorge is here three nights a week, three weeks a month playing the same old songs he’s played for decades: lots of country, folk and classic rock, “Feliz Navidad” regardless of weather or season. He looks the part of an old-school pub guitarist — deeply lined face, scruffy mustache — and sings in a gravelly baritone, almost always on key.

A week ago, a group of Catholic University alumni reconvened at the Irish Times to catch Papageorge’s fourth-to-last show. They called it “Papageorgepalooza.”

For Christine Carey, who graduated in 1997, it was her first trip to the pub since she moved from the District to North Carolina 10 years ago.

“It was exactly the same. It even smelled the same,” she says. “You walk back in and all your memories come true again.”

Dancing to Pete’s music on her 21st birthday. Meeting up with friends after work. The night she met her husband here.

The pub seems designed to promote that sort of nostalgia. Assorted old-fashioned posters crowd the walls and donated police patches cover every inch of space behind the bar. The tablecloths are made of the same green-and-white checkered plastic that was used in your summer-camp dining hall. The top rack of the liquor shelf is devoted entirely to bottles of Jameson.

Its patrons, too, remain consistent, in type if not in name: Catholic students like Carey, officers from various branches of law enforcement, congressional staffers.

There are even a few regulars who have been here longer than Papageorge, Dowling among them. The Dublin native, whose accounting office is around the corner, has been drinking here since the pub opened in 1978. He needed a D.C. bar where the Guinness was tolerable.

“It’s comfortable, everyone’s welcome,” Dowling says. “Sometimes even politicians come through . . .” he pauses, chuckles. “Maybe they’re not so welcome.”

Dowling can recall live acts before Papageorge, but none of them stuck the way he did.

“He came and just made it his show,” Dowling says.

Papageorge tells the story somewhat differently. More than a decade out of college and scraping together a living as an itinerant soloist and occasional band member, he’d had no grand plans when he dropped a tape off with the manager one afternoon in 1985, nor when he got a call a few weeks later, asking if he could play that night.

“I was hired for the weekend, and I really thought that was going to be it,” Papageorge says. “I guess it’s been a long weekend.” He shrugs.

Papageorge is like that. For a musician, he has few delusions of grandeur. He drinks water instead of beer during shows. He doesn’t gripe about never hitting it big or the drunk, unappreciative kids in the audience. He’s modest. So modest that when the Irish Times staff threw him a 25th anniversary party two years ago, he didn’t have the heart to tell them it was actually his 27th.

And he’s beloved. Brendan Kelly, second-generation owner of the Irish Times, was 11 when he met the guitarist. He bashfully admits that Papageorge was the adult he most looked up to.

“I just thought he was so awesome,” Kelly says.

But it was also Kelly who made the move to end Papageorge’s run here. It was a budgeting decision, the only one that made sense, he says, given the neighborhood’s changing demographics. The pub now does the majority of its business at lunch and happy hour — hours before Papageorge opens his guitar case around 9 p.m.

The Irish Times could only shut out change for so long. So, as manager Sean Ryan diplomatically put it, “We decided to move away from full-time live music.”

This is not retirement for Papageorge, though he isn’t sure what he’ll do with his newfound free time. Perhaps he’ll try his hand at full-time acting (he’s had small parts on various movies and TV shows, including “House of Cards”) or pick up more voiceover work (he’s the narrator for, among other things, the video game “Fallout 3”). He’s definitely looking forward to spending weekends listening to someone other than himself sing.

He and Kelly are also quick to make clear that he won’t be absent from the Irish Times for good: Papageorge has already been booked to play St. Patrick’s Day, Catholic University homecoming and other assorted events.

For the rest of the year, though, the pub’s soundtrack will likely come from an iTunes playlist. It’s a thought that makes old-timers scowl.

“You just stick the Internet into a speaker, there’s no atmosphere,” Dowling says. “Guys like Pete bring atmosphere.”

Mike McCann, who has been bartending at the Irish Times for more than a decade, is already steeling himself for the backlash.

“I foresee getting a lot of ‘Where’s Pete?’ questions for a good two or three years now,” he says. “It’s going to take a lot of time to get over missing him.”

But things move along.