When I combine 2 organ manuals, a mechanical and an electronical one into a single instrument, how would you setup the delay from the position of the organ player?
Let's assume the mechanical manual has an average delay of 200ms between pressing down a key and when the sound can be heard. Would you setup the digital manual to have roughly the same amount of delay or as little as possible?
I assume both sound sources are nearly in the same location.
You might delay the electronic component a bit, yes. But it won't need to be as much as 200ms. A mechanical ('tracker action') organ actually has less delay than you might imagine.
https://www.ingentaconnect.com/content/dav/aaua/1968/00000020/00000004/art00003
The disadvantage to this classic type of mechanism is that the keys can be heavy, and everything needs to be quite close to the console.
150 years ago pneumatic action was popular. It enabled larger instruments, and suited the Victorian taste for the bombastic. A disadvantage was sluggish response.
https://en.wikipedia.org/wiki/Tubular-pneumatic_action#Decline_of_usage
Today, tracker action is back in fashion, with electro-mechanical action where distance makes it necessary. Delay IS an issue, but it's acoustic rather than mechanical. Organs tend to inhabit large buildings, sections of a large organ may be mounted some distance from the console for dramatic or architectural effect. sound takes time to travel, and what the organist hears may be more reverberant than direct sound. or headphones Maybe organists should be provided with nearfield monitors, fed from microphones close to each rank of pipes! In practice they just hit the keys in time and manage to isolate their brains from the acoustic feedback!
Organ is not the only instrument where the player has to (often automatically and subconsciously) 'play early'. But not many have to deal with the delay from a unit at the other end of a sizeable church AND the earlier sound from more local pipes!
Also see: How does a pipe organist deal with latency or delay?
The best way to do this would be to make the delay from the electronic keyboard controllable so the player can choose whether to have a delay and if so, how much.
Don't you have your problem backwards? A mechanical keyboard opens the valves to the pipes. Its action is as fast as possible. Pneumatic and/or electric systems are the ones that introduce latencies due to intermediate mechanisms. They are avoided in modern organs because they remove the fine control of the player over the key attack. So unless you have one of the pneumatic monstrosities popular in the 19th century, there will be no need for delay. If you do have one of those, the delay will very much depend on just what kind of organ you have and just what kind of pneumatic lines have been laid over what distance. There is no general advice suitable then.
