The “Mighty Wurlitzer” organ at the Castro Theatre is not actually a Wurlitzer organ. It hasn’t been one since 2015, when the theater’s genuine Rudolph Wurlitzer Company organ was deemed too busted-down and replaced with the basic, two-keyboard electronic instrument that’s been at the Castro these last four years.

But the new organ is complete, and it’s currently sitting some 3,000 miles away in a warehouse in Zionsville, Pa. Destined to be the largest pipe-digital hybrid organ in the world, this colossus is stacked with seven keyboards, 800 “stop tab” keys, and 120 speakers that will fill the theater with glorious sound.

“The console is built,” says Jeff Rodman, a member of the Castro Organ Devotees Association (CODA), which is overseeing the fundraising and installation for this new modern marvel. Rodman expects the new organ — along with the 1,800 pipes that were built for it — will be shipped and installed “sometime next year, hopefully in the earlier part of next year. It’s a matter of finishing it and putting it together.”

The new Castro Theatre organ will be a combination of a classic orchestra organ and a massive digital-sampling machine, capable of all the old Wurlitzer tricks and thousands of new sounds, too.

“It will be the equivalent of the largest organ ever built,” says David Hegarty, the Castro’s staff organist since 1978, and the fellow who’s played that organ before just about every Castro movie screening you’ve ever seen.

There are two other organs of similar size in the U.S., neither of which is ever played much. Atlantic City’s Boardwalk Hall Auditorium Organ is the largest ever built, but it’s barely operational so it’s currently under restoration. Named for a long-gone department store, the Wanamaker organ at a Philadelphia Macy’s is the world’s largest functioning organ, but it’s only played twice a day for brief, 15-minute vignettes.

The Castro organ will match their size, and sit in a venue properly designed for organ performances.

“The new organ will be a showcase for great organists from around the world to play whatever their specialty is,” Hegarty tells SF Weekly. “We thought San Francisco deserved that kind of fame and attraction for organists around the world.”

The new organ will be able to do everything the old Wurlitzer could, only with a near-infinite number of new audio tricks up its sleeve.

“The Wurlitzer was strictly a theater organ,” Hegarty says. “It did very well what theater organs are supposed to do: Play popular standards to accompany silent movies in an orchestral way. But I’m interested in the whole range of organ music. I wanted an organ that could go way beyond the limits of what the Wurlitzer gave us.

“The idea of the ‘Mighty Wurlitzer’ came from the fact that most theater organs in the country were Wurlitzers. We’re not abandoning that by any means. We’ll be adding pipes to the instrument that are legitimate Wurlitzer pipes, and digital samples of other Wurlitzers, making this a far bigger Wurlitzer than the one that was in here.”

This will actually be the fifth organ that’s sat on the Castro Theatre dais since the theater opened. The first was from Robert Morgan Organ Co. in 1922. (“That was pretty small. It was two keyboards and 13 sets of pipes,” Hegarty says.) House organs became obsolete when the “talkies” came to movie theaters, although the Castro’s wasn’t removed until the 1960s.

The theater installed a Conn electronic organ in early ’70s. It was really no greater than organs you would (occasionally) find in someone’s living room in those days. The Mighty Wurlitzer we remember was installed beginning in 1978, and took about five years to complete, as that instrument was essentially a Frankenstein’s monster consisting of parts from other abandoned Wurlitzers from around the world.

It lasted until 2015, when Hegarty donated one of his own units as a loaner.

“One of my students died and left that organ to me,” he says. “I moved it straight from her house into the theater. She would be amazed.”

The new organ will be able to reproduce the full symphonic array of sounds, even string and brass instruments. Digital samples will allow it to replicate Wurlitzer organ notes, plus just about any instrument under the sun.

“It can cover jazz. It can cover theater performances. It can cover blues,” Rodman says, adding that, for the ’60s soul sound, “It’s got a Hammond organ stock.”

Looking closely, the organ not only has seven keyboards, but also 837 “stop tab” buttons that each create a different sound. What you don’t see is the giant array of new pipes that still has to be installed in the guts of the Castro Theatre.

“This one will be approximately 400 ranks of pipes, as opposed to the 21 we had before,” Hegarty explains. “The audience won’t see much of any change here, the pipes and the speakers will be in the chambers.”

More than 100 speakers will help achieve sonic magic unlike anything you’ve heard in a concert hall.

“It’s being designed to create a variety of environments, from small rooms to large cathedrals,” Rodman says, explaining the reverberation, resonance, and echo techniques the organ will employ. “To do that, there are 120 speakers distributed around the periphery, around the front edge of the balcony, with a complex electrical system to drive those.”

And for good measure, the Castro will also need a new hydraulic lift to elevate this mammoth 1,800-pound organ before each performance.

All of this will obviously cost a great deal of money. CODA projects an overall cost of $1.3 million, and they’re about halfway to that goal. You may have already contributed, whether you know it or not, by attending one of the Castro’s movie sing-along shows.

“Our nonprofit gets a cut every time they do a sing-along,” CODA member Adrienne Hirt tells SF Weekly. “We get a dollar for each adult ticket.”

Those sing-along donations have brought in about $100,000, but CODA has plans to score bigger contributions. “There are naming opportunities for larger donors,” Rodman says. “There is the potential for the pipes or the console or the whole organ to have someone’s name,” which would then appear on concert programs or onscreen before shows.

The restoration of the Castro Theatre organ is part of a larger strategy for the venue to double as a performing arts center, with the new organ as its focal point.

“There will obviously be a lot of musical events here featuring it that we’ve never had before,” Rodman says. “Because there hasn’t been an instrument like this before.”

The organ is not an especially popular instrument in contemporary music, and single-screen movie houses are practically extinct. The new Castro Theatre organ could revitalize both of those dying breeds, or at least interest in them. And you can still help the Castro pipe up like no theater ever has by being an organ donor to CODA’s fundraising efforts.