On a cloudless Friday, some three blocks uphill from the eastern sweep of Seattle’s Green Lake, a gleeful postwork throng descends on Latona Pub to let off some early weekend steam. The bar dates to 1987, when Bob Brenlin—still an owner—bought an old “boarded-up tavern” and gave it the first of many remodels. Today the floor-to-ceiling windows and plush color palette make it one of Seattle’s hush-hush gems.

Of course, you wouldn’t call the Friday scene hush-hush. It’s more like a malty beehive. And it’s anchored each and every week by bassist Phil Sparks, who from 5 to 7pm leads what is almost certainly the longest-running jazz gig in town—even if Sparks himself isn’t quite sure when it started.

By virtue of its dual rhythmic and chordal duties, the bass is necessarily the most dependable piece of a functioning jazz ensemble. And Sparks, 70, is one of the most dependable bassists in the Seattle area. A founding member of the 30-year-old Seattle Repertory Jazz Orchestra, with recording credits ranging from saxophonist Hadley Caliman to drummer Jerry Granelli, Sparks moved to the Green Lake neighborhood in 1985, two years after relocating to the PNW from Colorado. “In my mind,” he says, “I believe the first people to play music at Latona Pub were my wife [Rosemary Sweeney, a singer] and myself.”

Sparks often adds caveats like “in my mind” to his time at the pub. When you play as many concerts as he has, with as many different musicians, things can get a bit fuzzy. What’s certain is this: His Latona Pub residency, which began on a weekly basis sometime in the aughts, has become an absolute Seattle fixture. It’s not just a boon for the neighborhood. On some Fridays, it feels like it is the neighborhood.

Tonight the band is a rhythm-heavy trio of Sparks, Cornish professor Greg Campbell on drums, and Seattle standby Leif Totusek on guitar. With Totusek playing the melodies, they hum through a classic first set. Thelonious Monk’s “Let’s Cool One,” Sonny Rollins’s “Oleo.” Despite the pub aesthetic—the room’s spiritual crux is a Mariners-capped pig head—Sparks’s music gives the space a dinner-club ambience. It’s loud enough to set the mood but quiet enough for conversation, just how the band prefers it.

The crowd is largely of Sparks’s generation and leans gray-ponytail-Folklife. It’s filled out with some attentive young jazz artists and couples on dates. Passersby see the good time through the windows and swing through, squeezing into standing room—tables tend to fill early with regulars like Stetson-wearing Paul Zemtseff, who migrates between his group and the front of the audience to take videos when something catches his ear.

“I’ve seen Phil hundreds of times,” Zemtseff says, before putting a hand to his chin and wondering, honestly, “Maybe a thousand?” This sounds absurd, but it’s not impossible given that Sparks has plugged away here every week for something like two decades.

Sparks organizes his Latona calendar each year based around the availability of regular bandmates like Totusek, who claims he’s played here some 300 times. He also has a lengthy backlog of alternates to be called at a moment’s notice. In a music-rich city like Seattle, throwing together a jazz group isn’t the most difficult thing in the world. But doing it every week for 20 years? That’s both a monumental feat of perseverance and a true service to the community.

Sparks says he’s received “many comments” over the years about how important the gig has been in fostering local identity. Wherever he plays in Western Washington—Everett, Snohomish—people recognize him from Latona Pub. “I’ve been very lucky to have a few regular gigs over the years,” he says. “I played with [saxophonist] Floyd Standifer at the New Orleans for over 20 years. And with [vibraphonist] Susan Pascal for 10 years at Plymouth Congregational Church.”

During prolonged musical residencies, a venue can take on the aspect of its sitting band, and vice versa. Think the Beatles at the Cavern Club, or Duke Ellington at the Cotton Club. With his soft-spoken aura and mellow instrumental tone, Sparks is both icon and avatar at Latona Pub. “Friday is something people look forward to,” says pub owner Brenlin. “Phil is an inspiring talent. People come from all over to play with him.”

As for the central question: How long, precisely, has Phil Sparks Friday been a thing? The bass player ponders it for a bit and guesses 2009. But then he remembers that Hadley Caliman, who passed away in 2010, used to be a regular bandmate. “So that’s not right.” Totusek pegs it at 24 years. Ish. Sparks waves the guitarist off, not out of disagreement with his answer but with the question itself.

“I try not to nail it down,” he decides with a grin. “It’s bad luck.”