The man behind the organ at the Rockefeller Memorial Chapel has been pulling the stops for 25 years

A visit to see Thomas Weisflog at the University of Chicago’s Rockefeller Memorial Chapel is like stepping into the scene in “The Wizard of Oz” in which Dorothy, the Tin Man and their companions meet the wizard.

A great forest of zinc pipes — the longest of them stretching 16 feet — soars along the east chancel wall. All is quiet until Weisflog, hidden behind an oak consul, goes to work, his fingers stroking keys and pulling stops. He reaches for a stop labeled “tuba mirabilis.” Thunderous notes fill the chapel, rattling the woodwork.

Weisflog has been entrusted with the chapel’s Opus 634 organ for 25 years as of Oct. 1.

To the layperson, the organ’s four keyboards and dozens of stops — from the “chimney flute” to the “flugelhorn” — might seem as puzzling as a Boeing 747 cockpit would be to someone who isn’t a pilot.

But Weisflog, 79, knows how to prod and caress the instrument to create sounds that stir the soul and tickle the imagination.

He plays a few notes using the “orchestral oboe” stop, conjuring a Middle Eastern bazaar.

“I call it the belly dancer,” says Weisflog, who stands 5 feet 6 inches tall, is bald and has a rubbery face, which comes in handy when he wants to play the organ and talk at the same time.

Weisflog began playing the organ when he was 15. He first tried out the Rockefeller Chapel organ in 1968, when he was a graduate student in chemical physics. He began taking organ lessons at the university, eventually quitting physics. He was appointed university organist in 2000.

The instrument he calls “my baby” was built by Ernest M. Skinner, who is considered the master of American organ building. Completed in 1928 for $76,500, the Opus 634 has 8,565 pipes — both wood and metal — with a “speaking length” ranging from 5/8 of an inch to 32 feet. The speaking length refers to the distance between the horizontal slit-like “mouth” of the pipe to the opening at the top.

Skinner, who died in 1960, was an eccentric type, according to Weisflog, who never met him but has researched his life.

“He would measure the space [for the organ pipes] with his umbrella,” Weisflog says.

He demonstrates a few of the organ’s pyrotechnics, then potters off in suede-bottom shoes — which allow his feet to slide from one pedal to another — to a narrow oak door near the wall of pipes. He makes his way up a tight, spiraling staircase that brings to mind one of Harry Potter’s nighttime explorations through Hogwarts School of Witchcraft and Wizardry.

“When I first came here 25 years ago, I could run up and down these stairs,” Weisflog says.

At the top step, Weisflog guides his guests into a space crammed to the rafters with pipes of different lengths and circumferences. He lifts a small wooden one, puts it to his lips and blows, producing a flute-like sound. Only he is allowed to remove pipes, he says.

During the academic year, Weisflog plays for Sunday services as well as at 4 p.m. every Tuesday for the “Tea and Pipes” half-hour concerts — the first of the season, an annual event on Sept. 30 called “Pets and Pipes,” in which the public is invited to bring a domestic animal of choice. It’s usually dogs, maybe some cats, with the occasional snake or turtle.

“They are mesmerized by the sound,” says Weisflog, who started the event four years ago in part for his own amusement.

Between playing, teaching students and taking care of other odds and ends, Weisflog says he’s in the chapel four to five days a week.

For a fee, he also plays the organ for weddings. He’s not fussy about what he plays.

“My philosophy is: It’s their wedding,” he says. “This isn’t a church with a doctrine that says you can’t have ‘Here Comes the Bride,’ or you can’t have pop music. If they want poppy-woppy music, I simply say, ‘It usually doesn’t work well on the organ.’ But it’s their wedding. They can have what they want.”

The chapel seats 1,500 people. Over the years, guests have included Chicago mayors and Illinois governor, as well as former President Bill Clinton.

Weisflog says he doesn’t think he’s ever played for former President Barack Obama — unless he sneaked in without him noticing.

“I always envision him coming, and I would play ‘Hail to the Chief’ on the big trumpet stop at the back,” Weisflog says.

The audience is usually small for the 11 a.m. Sunday services, except on big holidays.

“We just play for the glory of God,” he says.

Sometimes, visitors wander through the chapel when Weisflog. On a recent day, a couple from Brazil hoped to have a look inside. The chapel was closed, but Maurice Charles, the chapel dean, let them in. At some point, the man stopped to talk to Weisflog.

“He said, ‘This is my wife’s birthday,’ and Tom said, ‘Oh, wonderful!’ ” Charles said. “And he turned to the organ consul, and we serenaded his wife. That is Tom. Tom is the perfect university organist.”

Weisflog enjoys the generally solitary nature of what he does. Organists are a “rather unusual breed,” he says.

But is he really alone? Does he ever feel closer to God when he’s playing, say, a Bach fugue?

“Yes, you feel like you’re doing something really special,” Weisflog says.

Sometimes, he says, his work “transcends” the self.

The organ might be his “baby,” but Weisflog is generous with the multimillion-dollar instrument. A few years ago, this reporter’s 80-something grandparents came to Chicago. I called Weisflog and asked whether my grandfather, a lover of organ music, could hear him play. Weisflog arranged a private concert and even invited my grandfather to have a go. My grandfather, who liked to play the organ at home while enjoying a glass of Scotch whiskey, politely declined, something he regretted for years afterward.”

But Weisflog says most people say yes when he offers them a chance to play.

“Sometimes, the people will sit down, and they really don’t quite know what they’re doing,” he says. “And I just say, ‘Do not strike the keys hard.’ And: ‘We do not want dirty street shoes on the pedals.’ I’ll pull stops for them.”

Among Weisflog’s favorite pieces is Czech composer Leos Janacek’s “Glagolitic Mass,” which was first performed in 1927.

“It has a huge organ part in the middle,” he says. “The mass was composed for the outside, where the trees of the forest would look on and animals and such. So it has sort of a wild flavor to it”.

He gives a cheeks-puffed, growling rendition of the organ solo part: “Ba-da-da-da-da-r-r-rup!”

That’s the point in the piece at which, he says, “The organ goes completely mad — full organ.”

These days, he has a little numbness in his feet. And he no longer can hear the very highest musical notes. But Weisflog has no plans to step from a job he feels fortunate to have.

“As long as my health holds out,” he says. “It’s a unique position. I’m surprised I haven’t been assassinated for people who want my job.”