He probably won't greet you at the door. His name might never be on the marquee. But the next time you visit Birmingham's Alabama Theatre, you might want to stop, however briefly, and pay silent tribute to a man named Larry Donaldson.

Donaldson, a retired engineer with a steel-trap mind and a taste for history, has been a hands-on volunteer at the theater since 1969. He looks a bit like Kriss Kringle (a bonus at this time of year) and maintains his own type of Santa's workshop in the backstage labyrinth.

"It has been a lifelong hobby," says Donaldson, 67. "If I'm not gone on a trip, I'll spend 40-50 hours per week here."

His primary interest, the theater's magnificent Wurlitzer organ, led Donaldson to the Alabama at age 19. But over the past half-century, he's become an expert on the theater's operating systems -- lighting, air-conditioning, heating, plumbing, stage rigging, electrical and more -- and mastered the intricacies of the historic building, top to bottom.

"Larry is an unsung hero of our organization," says Danny Evans, longtime board president of Birmingham Landmarks Inc., a nonprofit that owns the Alabama and the nearby Lyric Theatre. "He knows as much about the organ and the physical plant of the Alabama Theatre as anybody. He knows all the systems, the wiring. He's smart as can be. He's just invaluable."

In an era when nonprofit organizations struggle to keep volunteers active for five or 10 years, Donaldson can claim nearly 50 years of involvement at the Alabama.

He lists himself as "organ crew chief" on his LinkedIn profile, pointing to an enduring fascination with the complex, finicky instrument affectionally known as Big Bertha. Many regard the pipe organ, built in 1927, as the heart of the theater, and Donaldson leads a team of eight people who spend their Saturdays engaged in painstaking labor, repairing and maintaining it.

"From a little kid, I was infatuated with organs," Donaldson says. "I didn't know the difference between an electronic and pipe organ, but I had been here as a 3-year-old and saw Stanleigh Malotte and the organ coming up out of the floor. I was sitting in the mezzanine and I saw the console going up and down, with him playing this massive instrument. It just fascinated me. I was infatuated with the organ from then on."

Take a tour of the Alabama Theatre with Donaldson, as AL.com did recently, and he immediately heads for the Mighty Wurlitzer. As Donaldson explains it, the elaborately decorated console (the part audiences see, with its keyboards and pedals) is just one part of the organ, which also has three chambers tucked into the theater's innards.

Those chambers hold pipes of various sizes that provide specific sounds -- violins, tubas, oboes, sleigh bells, bird whistles and much more -- and actual instruments, such as a piano keyboard, drums, cymbals and a xylophone, that play when triggered by the organist.

"On a theater organ, you orchestrate, just the way you would for an orchestra," Donaldson says. "On this phrase, the clarinets play. On this phrase, the flutes play. ... It's such a unique sound. You don't get it anywhere else."

He's clearly in his element moving through the organ chambers -- cramped, asymmetrical spaces that require him to climb narrow ladders, maneuver in tight crevices and walk on wooden planks over sheer drops -- and when Donaldson is there, explaining the functions of the pipes and proudly pointing to real instruments, he seems like a combination of Mr. Fix-It and the Phantom of the Opera. (Think overalls and a screwdriver instead of a mask and cape.)

Donaldson also presides over a cluttered organ workshop on the theater's fourth floor, directing volunteers surrounded by leather and glue, tools and machines, spare parts and scavenged pipes. He's quick to emphasize the group effort that keeps Big Bertha running, but few would argue that when it comes to organ upkeep, Donaldson rules supreme.

Larry Donaldson leads the organ crew at the Alabama Theatre. He offers kudos to the volunteers on his team: Tom Cronier, Andy Fox, Lex Sorensen, Karl Sorensen, Bob Yuill, Sabrina Summers, Andy Gallien and Pat Seitz. (Joe Songer | jsonger@al.com)

"The organ is beautiful in front, but take the back panel off and it looks like a robot," says Brant Beene, executive director of Birmingham Landmarks, who's worked with Donaldson since 2009. "The entire thing is like a Rube Goldberg device. Larry's into the mechanics of how this machine works, and he appreciates the way it works. I think what Larry loves is the contraption."

It's safe to say that Donaldson can troubleshoot every inch of the vintage organ (technically known as the Wurlitzer Opus 1783, Style Publix 1) after spending 48 years on its care. But can he play it?

"I know how to play the organ. No, I can't play the organ," Donaldson says. "All I could play would be church organ, not theater. It's a totally different technique."

Donaldson's ears are finely tuned, though, and he admires the folks who've coaxed great performances from the organ during its 90-year tenure at the Alabama. (The theater opened on Dec. 25, 1927, and the Mighty Wurlitzer was a dazzling part of the show.) In fact, Donaldson devised a computer system to record and replay performances on the Wurlitzer, so organists such as Tom Hazelton, Jim Riggs and Gary Jones can be heard by future generations.

'I got infatuated with the building'

So how does a teenage boy transform into a devoted volunteer at the Alabama Theatre? For Donaldson, then a student at the University of Montevallo, all it took was an invitation from his mentor, Jay Mitchell, choir director at First Lutheran Church of Birmingham.

"I was in the choir; I was also studying organ at the time," Donaldson recalls. "I was the assistant organist there. He was the one who said, 'You ought to come down and see what we're doing. We've got a little crew started to work on the organ. You might be interested in seeing what we do.' So I came down with him.

"The first thing I saw was, he couldn't get the spotlight to work properly. So I went back and started -- my father was an electrician; I worked with electricity all my life -- so I started working with the lighting board, to see if I could get his spotlight to working. And then I said, 'My gosh, what this lighting board was capable of doing in 1927.' And that got me going.

"I started working for the manager of the theater after midnight, repairing the old lighting board so that he could get more of the architectural lighting to work for the audience. And then, being engineering-minded, I got infatuated with the building," Donaldson continues. "How was it built? What was all this stuff for? Why was this stuff done this way in 1927, which made little sense in 1969-1970? And then I was trying to figure out all the different things about the building."

Within a few years, Donaldson had earned his own key to the theater at 1817 Third Ave. North, along with the responsibilities of organ crew chief. (Choir director Mitchell moved to Huntsville in 1973 or 1974, he says, and the theater manager trusted him.)

Donaldson became a member of the Alabama chapter of the American Theatre Organ Society, and joined the board of directors of Birmingham Landmarks in 1987. His interest in the theater never waned, even when his schooling -- Donaldson graduated in 1973 from the University of Alabama -- and his career as a chemical engineer took him out of town.

Although he lived in Tennessee and Georgia for about 40 years, Donaldson made the trip back to Birmingham every weekend, settling into a routine that allowed him to continue his volunteer work at the Alabama.

"Larry loves the theater, there's no question he does," says Evans, the former board president. (He retired a few months ago, after a 30-year tenure.) "We used to have open houses at the theater, where people could come and see the backstage stuff. Larry's a great tour guide."

Donaldson says it took years for him to become accustomed to the internal maze at the theater, exploring its depths and trying "not to leave footprints." These days, he navigates through the building with practiced ease, pointing to many practical projects he's spearheaded.

"It's not all glamorous," Donaldson says, smiling.

Currently, for example, he's overseeing the installation of a new air-conditioning system, and making sure lights at the theater are switched from incandescent bulbs to more efficient LEDs.

Donaldson's to-do list has included reconfiguring vents at the top of the building, working on sump pumps and sewers, using computer programs to regulate the heating and cooling systems, solving logistical problems with the concession stands, clamping off a steam leak in the generators and devising ways to run wiring behind the theater's delicate plaster.

"Larry doesn't mind getting his hands dirty at all," says Beene, the Alabama's executive director. "But with so much to do at a 90-year-old theater, he can't do it all. His role has sort of become our facilities manager. He knows what has to be done, and we hire it out. He always does that with an eye to historic preservation. His contributions have not just been aesthetic, which is very valuable to us, but he's saving us money in utilities."

According to Beene, Donaldson's generosity to the theater manifests itself in other ways, via light bulbs and hardware and computer panels.

"Anytime Larry's working on something and he knows the theater needs it, more often than not he'll purchase the item and donate it to the theater," Beene says. "I can't tell you how many times he's done that."

Does Larry Donaldson have any other hobbies, aside from his interest in the Alabama Theatre? Well, he's been known to attend the World Beard and Mustache Championships, with others who appreciate the hirsute. "I had a beard two weeks before my 21st birthday, and that's the one I've got now," Donaldson says. "I never shaved it off." (Joe Songer | jsonger@al.com)

'I get a little bit anxious'

Donaldson moved back to Birmingham when he retired in 2014, making it easier for him to spend time at the theater and give the Wurlitzer frequent doses of TLC. He tends to shrug off comments about his wizardly ways -- Beene says it would take five people to replace him if Donaldson ever quit -- and deflects praise with succinct, self-deprecating humor.

"I stay busy here," Donaldson says. "It keeps me from sitting home watching 'Wheel of Fortune.'"

Still, he acknowledges that his particular combination of interests, talents and skills would be tough to duplicate. Donaldson's specialty as an engineer is control systems, but as Evans and Beene will tell you, he's become the go-to guy for the theater in countless ways.

"I've got several different expertise that you're not going to find in one person," Donaldson says. "It's not something I intended; it just happened that way. You're not going to find somebody who has control systems, is involved with the building and involved with the organ. ... I know there will be somebody behind me to take care of the organ. I get a little bit anxious at: Is there somebody coming along behind me that will care as much?"

Donaldson's life has become so intertwined with the theater, he's been entrusted with the original blueprints, drawn in pen on linen by architects Graven and Mayger. These precious documents are carefully stored in the organ workshop, and Donaldson has been known to pore over them, marveling at their detail and precision.

Consider, too, that he plans his vacations with organ research in mind, attending annual conventions of the American Theatre Organ Society and conferences organized by the League of Historic American Theatres. Donaldson also travels the globe with Pipedreams, a group that's obsessed with pipe organs and affiliated with public radio.

"Larry is a very good ambassador for the theater," Beene says. "He makes great contacts, shares ideas and compares information."

Right now, Donaldson's staying close to home, helping the Alabama Theatre to prepare for the unveiling of its new sign on 18th Street. The theater secured a $120,000 preservation grant this year, allowing it to install a replica of a vintage sign that's been missing since the 1950s.

Donaldson, who's overseeing the sign project, says he'll likely be the one to flip the switch when the sign is unveiled at the stroke of midnight on New Year's Eve. The Alabama will present a concert earlier that evening, to celebrate the theater's 90th birthday and welcome 2018 in style.

As usual, Donaldson will work his magic behind the scenes, making sure the sign glows brightly to mark the occasion. In his view, the Alabama Theatre is the real star of the show, and a caregiver can take satisfaction in a job well done.

"I'll be here as long as my knees will handle it," Donaldson says, when asked about his plans for 2018. "As long as they want me, and I can."