A little knowledge of how our pipe organ works can go a long way to keeping it working correctly.
"Cypher" (also spelled "cipher") is the term organ builders use to describe a "stuck note" -- the continuous sounding of a pipe after a manual or pedal key is released, a malfunction most often caused by dirt -- either in the primary valve or under the pipe.
Dirt can find its way into any valve and prevent it from working properly; every valve on every note must seal properly, and some of the action valves have to seal in both open and closed position; if dirt is on the magnet side of the primary valve (armature) it will cause either a cypher or a dead note (See blog, Dead Notes); most secondary valves are double action, thus dirt on either side will cause a problem; the 3rd valve in the series is typically the one that sits under the pipe, and dirt there will cause a "partial" cypher.
If the organist is specially trained in organ building, and there happens to be dirt cypher in the primary valve, it may be possible to locate it the same day, unscrew the armature cover, and extract the dirt.
NOTE: Organists need to be able to determine what caused the cypher before they go around unscrewing armature covers; armatures are small, and the wind pressure can cause them to go flying only to disappear on the floor of the organ somewhere, or maybe fall through a passageboard to the level below; in that event the organ will have a permanent cypher, and the organ technician MUST be called.
There are 2 kinds of cyphers in pipe organs: 1) the simple (or wind) cypher, which is generally caused by dirt, less commonly by broken magnets or armatures or, even more rarely, valve problems, and 2) the relay cypher, which has the same root cause and results in a continuous electric charge to one or more chest magnets, thus causing the respective pipe(s) to sound.
Aside from a potential wiring issue, organ pipes and wind chests are sensitive to temperatures and humidity -- and, right on time, with the onset of cooler weather, many of us experience a stuck note.
Sometimes we can un-stick the pallet from the console; we can try tapping the key over and over again, repeatedly sending an electrical signal to the magnet which allows pressurized air to enter and leave the chest below the stuck pipe; the pressure differential causes a pneumatic within the chest to first collapse, then recoil when the key is released, pulling the pallet open and closed underneath the stuck pipe.
We can also try mashing down a bunch of keys at once, with lots of stops drawn; this both sends a signal to the pipe and takes some of the air pressure off that particular note because it's going to a lot of other notes.
Both of these attempts speak to trying to wiggle the pallet on the stuck note, and sometimes it will work -- but, obviously, it generally cannot be done in a performance situation.
The obvious quick fix is: just don't use that stop ... try to find it as quickly as you can and keep its drawknob or stop tablet retired; when that isn't possible, the entire manual division may have to be ignored for the time being and some other manual(s) used.
If the ladder must come out for a trip to the inner sanctum there are some temporary measures that can be taken; in the case of a flue pipe, a piece of paper or cloth handkerchief or dish towel or rag can be gently stuffed into the mouth of the pipe ... OR ... the pipe (if it's small enough) can be gently pulled out of the wind chest and left for the technician to fix; in the case of a reed pipe the tuning wire can be shoved down into the boot to close off the reed over the shallot completely, thus creating a "dead note" until the technician can fix it.
Finding the right pipe requires a little detective work, but it isn't rocket science; we can start figuring out which division it's in by closing the Swell shoe; if only the Swell division is enclosed and the volume changes, it's coming from there; the same holds true with the Choir, Antiphonal, Echo, or any other enclosed division; working the shoe which controls those divisions will pinpoint the division; if there's no change in volume, then the problem is in the Great, Positive, Pedal or some other unenclosed division.
When the ENTIRE organ is enclosed or unenclosed we can try the divisional tremulants; if the tremulant causes the cypher to shake, we've found the correct division.
If the cypher is just a whimper it's probably a piece of dirt in the valve under the pipe; if it's sounding full open it's probably in the key action itself.
If the cypher dies away by degrees when the blower is turned off there's a physical obstruction -- dirt -- holding a valve open; if it stops suddenly, it may be an electrical problem.
Knowing what kind of chest action(s) are in the organ is important to know when trouble-shooting cyphers:
A tone channel chest has only one valve per key on the keyboard; in this case ALL pipes on a certain key will cypher, although some may be more sensitive than others; if let's say tenor C13 is cyphering on the 4' Octave but then it goes away when the 8' Principal is drawn, the second stop will bleed off the air, and the sensitive tenor C13 of the 4' no longer gets enough air to speak; the tenor C pallet is still cyphering, however.
On a pitman chest there are several valves for each note; individual pipes can cypher if there is dirt under the pipe valve, but if all the pipes cypher the dirt is in the key action, probably on the little armature.
We can know if it's a metal or wooden pipe from the tone color (timbre) of the cyphered pipe, and we can know its approximate size from the octave where the cypher is located.
It helps to be familiar with the general pipe shapes and the sounds they produce -- diapasons, strings, open flutes, stopped flutes, color reeds, chorus reeds, etc.; the quality of tone will tell us what to look for.
We try to match the pitch by playing various keys on the keyboard; this is done slowly so we can keep track of the right key, since tapping it may fix the cypher; when we're not sure which key we pressed, then the builder doesn't always know precisely where to look to find the problem; if the problem can't be reproduced, neither the organist nor the technician can fix it.
We try to find the right stop, and thus the right pipe, by turning off all the stops; if the cypher goes away, we make a mental note of it; we then go through all the stops one by one to determine which one causes the fault.
If turning off the stops doesn't make the cypher stop, we can still go through the stops one by one to find which stop is cyphering.
Once the division is located and we know how to get there, we might carefully climb inside; we DO NOT start touching the pipes to find the leak; this will knock them out of tune; we use our ears to find the general area and then, if possible, start blowing air or dragging a dollar bill across the pipe tops until the sound wavers; in a larger flue pipe a finger can be held close to the pipe's mouth or a piece of paper can be used to partially block it; when the sound wavers, we've found the cypher without incurring a huge tuning bill.
We need to be careful not to move tuning slides while looking for a cypher; touching the top of a pipe, especially moving the tuning slide (or stopper, if it's a stopped wooden pipe, cap if it's a capped metal pipe), can knock it out of tune.
There are some safety concerns if we find ourselves doing this: well meaning people can get seriously injured if they don't know what they're doing when they're crawling around an organ chamber searching for a cyphered pipe.
Firstly, if it's a loud stop, we need to protect our hearing and either stuff our ears with lambs wool ear plugs or wear standard external ear protection before entering the organ chamber; big reeds on high pressure wind have a tendency to cypher more easily, and crawling around for several minutes approaching a pipe like this without ear protection can be deafening and lead to permanent hearing loss.
Secondly, we need to use enough light; when it comes to searching for something, we can't do well what we can't see well.
We need also to be careful and deliberate to keep our balance on ladders and when navigating wooden passageboards; falling into a crowd of metal organ pipes from high above can kill us.
When we're crawling through an organ chamber we need to remind ourselves NOT to engage in stunts like standing on top of the largest quadrangular wood pipes so someone can photograph us; this can be the cause of a very serious fall.
A pipe organ chamber is no place for reckless behavior just to be "cool"; stupidity is often deadly.
We need to wear rubber sole shoes and refrain from going into the organ chamber wearing our organ (leather soled) shoes; organ shoes are made to slide on pedal keys, not grip wooden planks or the rungs of ladders.
Above all, stay safe.