When Jay Converse dug his tuba out of mothballs a few years ago, he was hoping to fire up the ol’ oomp-pa-pas again and whip his middle-aged lungs into shape for a college reunion.

His wife had other ideas, he said.

“You’re not going to play that thing in the house?” she asked him.

So Converse saddled up the big brass horn, went out into the street in his Fairfax County suburb to play, and Tuba Guy was born. Since then, Converse has been tootling around the Kings Park townhouses and beyond, to the delight — mostly — of neighbors, passersby and motorists.

Lately, his walkabout jam sessions have taken on the character of training as he prepares to enter a marathon, although he has not decided which one. With a Facebook page and a growing number of fans following his progress, the question is not only whether he can hack the distance, but can he handle the local fame?

“I’m just letting it flow,” Converse, 55, said after wrapping up a typically peripatetic practice last week.

Before morphing into Tuba Guy, he was Milton Jennings Converse III, or Jay, and just another computer whiz living in the Northern Virginia suburbs with his wife of 34 years, his three children and a cat named Miles.

Then came the 30th reunion of the University of Virginia Pep Band, a zany troupe that once insulted West Virginia’s governor during a football game against West Virginia University with a hillbilly skit. Converse became the pep band’s poster boy, literally, after a newspaper snapped a picture of him and his tuba, which was decorated with a purple, fur-lined toilet seat.

As a founding member, Converse wanted to play his best, much to the alarm of his family.

“If he was in the basement, you could hear it all the way upstairs,” his wife, Elise, 60, recalls. “And I’m sure our neighbors hated it, too.”

“It doesn’t have an indoor voice,” he admits.

His wife denies forcing him — and the tuba — into the street. She says he came to his senses.

“I know that destroys the myth,” she says.

Converse has some traits you might expect from a one-man band: lots of energy (“hyper,” as his wife and children put it) and a very healthy ego. He has tormented his children with ukulele recitals and such excessive holiday displays that neighbors called him Clark Griswold, the holiday-crazed character played by Chevy Chase in “National Lampoon’s Christmas Vacation.”

He also plays at the community pool during Fourth of July festivities, usually while standing on the diving board in red, white and blue regalia.

His daughter, Rachel, said she used to have “Cool Mom, Lame Dad” contests with classmates at Virginia Commonwealth University and often came away a winner.

“I kind of tell people, ‘Oh, God, my dad is so embarrassing,” Rachel, 21, said. “But really, it’s just kind of funny. My friends think it’s awesome. They’re his Facebook fans and think it’s hilarious.”

Before his walk this week, Tuba Guy suited up in a pair of cargo shorts, a Guiness Ale T-shirt, running shoes and a stars-and-stripes kerchief. He donned the 30-pound tuba, which is accessorized with a pink propeller, a TUBA license plate, and several miniature American flags.

Then he was off.

“I know I’m walking slowly when the propeller stops spinning,” he said, as he fell into a steady 100 beats-per-minute stride.

Overhead, the sky was flawlessly blue, and step by step, the tuba revealed its many voices and moods, from B-flat thunder, to the mournful longing of an operatic tenor, to a flatulent honk at a passing car.

He was still warming up, blowing scales and noodling less than a block from his home on Braddock Road when he received his first smile, from a student leaving George Mason University. Moments later, a passing car sounded a fanfare on its horn, the first of many.

A few folks showed their appreciation by throwing money, including a cop Tuba Guy knows, who tried to sink coins in the tuba’s bell.

At intersections, Converse has to turn his whole body to make sure he can see oncoming cars, although it almost looks as if he’s saluting them. “You get used to dodging traffic,” he says. He has never had an accident.

Sometimes Tuba Guy riffs off whatever comes to mind. Other times, he plays identifiable melodies from Broadway musicals, pop songs or, this being Washington, military airs. He has worked up the intro to “Free Bird,” if only to answer the wiseacres who request it, but even he admits that it sounds very little like Lynyrd Skynyrd’s rock classic.

On the West side of Chain Bridge Road, Ellen Sherman paused from her spading as Tuba Guy passed. Sherman, 64, a retired teacher, said it’s not the first time she’s heard him.

“Hopefully, you have good soundproof walls,” Converse said.

“Oh, we love it,” Sherman said. “It’s a command performance.”

Then he was off again. The shiny silver horn coiled around him like a snake, catching the sun as he moved. He dabbled with the Beatles’ “Yellow Submarine,” Rodgers & Hammerstein’s “The Sound of Music,” “Anchors Aweigh” and, of course, “Yankee Doodle.”

Down a long, vacant stretch of road, the solitary tuba seemed to transform the world around it. Trees tossed in the breeze, cars whooshed by, and between the steady tramp of grit under his shoes and the rollicking notes of the tuba, he entered the strange solitude that can sometimes be found along the wide, grassy roads of the suburbs.