That’s Keith’s Hammond L100, which in the ELP days he used strictly for tossing around the stage. The C3 in his regular keyboard stack was the workhorse and, as @Francis_Vaughan said, was the heart of ELPs sound. The synths (except maybe the Yahama GX1 of later years) added color.
Correct, they don’t. (Retired Piano Technician speaking.)
You’re not wrong. A friend of mine used to work for Bedient and is still in regular contact with them, and they have more requests for pipe organs than they can possibly fill.
There’s a beautiful modern pipe organ at the Walt Disney Concert Hall, in L.A., designed by Frank Gehry, the building’s architect.
So they are definitely still being built.
A flue pipe on a pipe organ (as opposed to a reed pipe) has the remarkable property that its overtones are exact, despite the pipe itself having width, which one would expect to cause the overtones to sound at slightly enharmonic frequencies. Reed pipes only use the pipe proper to shape the sound and are not the primary source of the tuning (that is done by tweaking the reed.) So their overtones are no affected by pipe width either. Pianos need stretch tuning to cope with the problem of the harmonics sounding sharper than the fundamental. Pipe organs, very surprisingly (to me anyway), thus don’t need stretch tuning.
When it comes to temperament, it is pretty interesting. Historical organs were carefully tuned to specific temperaments, and this practice continues. Modern organs may eschew equal temperament as well. Depends on the music to be played.
How about a custom-made organ built into a house? « Into », not « in ». There was a fellow in our city who was enthusiastic about organ music and custom built a pipe organ into the basement, walls, and ground floor of his house. Did it over several years, constantly tinkering and installing new, old, and custom parts.
(@74westy , did you see this article?)
Not 'til now. Thanks!
Wow, I’ll remember this the next time I’m thinking about buying a bulky instrument (like an actual B-3 or Porta-B). “Hey, at least I’m not turning the house into an instrument!” Because, yeah, that’s totally something I’d do if given a free hand.
First question I asked Mrs P as she was reading the article to me : « Was he married? » « No, why? » she said. « Cause very few spouses would let you get away with that. »
Heheh, in this case, it’s a gradual escalation. She has a printing press, tools, cabinets for them, easels and some flat files. I have a bunch of instruments and their associated equipment. I’m not going to push my luck until we need to alter the building to accommodate larger canvases. 
The official residence of the Master of Student Houses at Caltech has a pipe organ built into it. I’ve seen it personally. It s pretty amazing: It looks like an ordinary house but tucked into some back rooms are a huge number of pipes.
ETA: Apparently it’s now used as the admissions office, no longer as a residence.
Next time my wife complains about my bass rig, I’ll show her that article.
My neighbor’s company is on that list. They do a lot of renovation work, as pipe organs need more than yearly (or even twice yearly) tuning.
Obligatory I Think You Should Leave clip:
What’s billed as the world’s largest hybrid organ is being built in San Francisco. “Hybrid” means it’s a blend of traditional pipes and electronics. I don’t know how many pipes it has but it does have seven manuals and ALL the stops. Seriously - 837 stops in this beast.
Maybe 837 was the plan for the Castro Theatre organ, but the maker’s site says 789 stops. Still a lot - the Wannamaker has “only” 464 stops.
Will it have some of those 128’ pipes? Can’t have enough bass.
The building isn’t that tall. I don’t think they’d even be able to fit 32’ pipes in the building, so that would be left to subwoofers on the electronic side of the organ.
And 4 Hz might be dangerous to the neighborhood. AFAIK, there’s only one organ on the planet with 128’ pipes.
You can get twice the length in half the pipe by closing the end. It affects the sound, but a 32’ pipe may not actually be 32’ long.