A short description of pipe organs

Organ: A Short Description of Pipe Organs

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Stephen Adams

A general perception is that pipe organs are more expensive to build and maintain than is perhaps worth while. It can sometimes seem difficult to justify expenditure, especially when compared to electronic instruments. We like to measure things in pounds and pence. Quite understandably, but go to your bank manager with a lump sum to invest and you will be asked how long you want to invest for. Investing in a good pipe organ is like this — it pays off handsomely in the long term. Many people who enquire about their pipe organs forget that the instruments may have given perhaps a century’s service already. It is on this premise that I write, in order to help qualify expenditure in the present tense. Also, it seems that there is no easily accessible information available to you, organists, clergy, etc. to help you come to an informed decision and to ensure you are getting value for money.

There are four main elements to a pipe organ, the casework, the wind system, the transmission, and the pipework.


The casework is what you see. Sometimes the casework is an integral part of the support structure, but usually not. Where this is not the situation, there will be some form of framework inside, to support internal parts of the organ. The casework displays pipes, some of which sound, others are just cosmetic (“dunmies”). Often, it is a mixture of both.

Variables with casework are many, but there’s not a lot of point in worrying about it, unless a case downright ugly. Generally, there are no moving parts in the case. Problems can include woodworm, joints coming apart, not standing plumb, damaged finish, faded pipes, etc. In the main though, it is not a troublesome area. Many people are of the impression that the visible pipes are the pipes of the organ. In reality they only constitute a small % of the total number.

Wind System

This system involves the production, storage, management and distribution of the compressed air. Nowadays most instruments use an electric blower to produce the pressure. Once the air is produced, it needs to be controlled, and this is done with robust valves which are usually trouble-free (although a fault here can render the organ entirely silent). After passing through these valves, the air is then stored in bellows (or reservoirs). There are various types and sizes of bellows. The one thing they have in common is a pliable air-tight material which is used as hinges, gussets and membranes. Usually leather is used, and this has a life span of 70 to 120 years depending on environment. Trouble is indicated when the organ starts to lose an unacceptable high and noisy amounts of air.


This deals with the release of air into whatever pipes the player chooses. It is by far the most complicated and troublesome area for the organ builder.

With this in mind, we must consider what is involved in making a pipe sound; it is choosing to deny or allow air to travel to the pipe. This is usually handled by large units called slider soundboards, which administer air to the appropriate pipes, according to what notes are being played and what stops are on.  Slider soundboards contain internal channels and other important elements to apportion or control the air. It is important that these units are in good condition. The main purpose of slider soundboards is to reduce the number of moving parts down to one set per note per division, rather than per note per stop. So a division with eight stops will require 56 moving parts (assuming a compass of 56 notes) for the key action, and 6 for the stop action with a slider soundboard.

When an organ is switched on, but not being played, no air should reach any pipes (if it is, there is a problem). As soon as an organist plays a note, a valve (called a pallet) is opened. This requires a certain amount of effort.

If you ever find yourself in the unenviable situation of being submerged under a water in your car, the advice is to open the window slightly and let the car gradually fill with water. If you attempt to open the door and are successful, you will be overcome with the rush of water. The work load of opening the car door has similarities to opening a pallet to let pressurised air travel to a pipe, as there is a sudden rush of air. This is known as “pluck” and can be felt at the keyboard if the action is a mechanical. The pluck can often be excessive in Victorian organs as they generally over-sized the pallets.

A common problem is where air leaks through uninvited; such a leak is called either a “whimper” or a “cipher”, depending on the extent of the leak. A whimper will give a distinct, quiet whistling sound whereas a cipher is where the note is being sounded with full volume. There are a variety of reasons for this, some serious and some simple to fix.

(As a side issue here, when a cipher occurs, it may only happen intermittently. For this reason, it is most helpful to the organ builder if the organist can record any details about the cipher, whimper, sticking note, slow note, etc. Details like: on what note is the problem? and on what stops? and under what conditions (e.g., were the couplers in use at the time? did it disappear when the note was played or tapped intentionally?)


The transmission is the means by which two things are controlled: (i) the stop action, which controls the sets of pipes to be used at any one time, and (ii) the key action, controlling what notes are to sound. There are three basic types of transmission (1) mechanical, (ii) pneumatic, (iii) electric.

Mechanical action

Mechanical action (also called tracker action) is both the most reliable and long lasting of all, provided it is well designed, made and set up. Nowadays organ builders have reverted to the old mechanical methods because they link the organist to the instrument in a more intimate manner. Problems can arise from excess of damp, which can make timber swell and metal rust, both effects causing friction. Excessive dryness can cause trouble too.

Pneumatic action

Pneumatic action uses air, either in “charge” or “exhaust” formats. “Charge” pneumatics is when a unit is inflated from within, while “exhaust” is when the inside of a unit is open to the atmosphere, and the space around the unit is pressurised, when it is then forced to collapse. These units (called “motors”) are connected to “pallets” or similar, which control the flow of air into the pipes. Pneumatic action became popular because it reduced the workload (the weight needed to play the notes) of the organist — it is a bit like power steering in a car. Also, it opened up new possibilities in terms of design/layout/accessories.

Problems can arise from both age and condition. Leather is the predominant medium here, and with age, it can either rot or become porous. Imagine blowing up a ten year old balloon? It will most likely burst or leak. Poor conditions include extremes of humidity, and polluted air. Low humidity will dry out leather, making it stiff at hinges and joints, and this will prejudice its operation — a bit like a book that has been closed for a considerable time and will subsequently not stay open.

“Charge” motors (see above) are usually sited out in the open. They are supplied with puffs of air carried via small-bore lead tubing. Over the years, this tubing can kink or become oval in its cross section, and this will reduce the power of the motor. Combined with porosity/leaks in the leather, this can result in slow and/or dumb notes. Everything in the chain of pneumatics needs to be in good condition.

To the uninitiated all this may seem terribly complicated. However, it’s really no different to any pressure - carrying equipment (e.g., water mains); it needs to be in good order. Generally, most pneumatics that were well designed and well laid out, are worthy of restoration.

Electric action

This took over many of the advantages of pneumatics, with the further attraction of only necessitating runs of light cable instead of cumbersome and sensitive air tubes. Older systems can be troublesome, as many (perhaps hundreds, or even thousands) mechanical sliding switches are used in the organ. These corrode, get dirty, and blacked from excessive arcing, and this can result in unreliable performance.

Electric have come a long way of course, especially when it comes to handling a large amount of information quickly. However, it is surprisingly limited in what actual pulling power can be produced economically. For this reason, electricity is often emp1oyed in the lighter-demanding but more- complicated initial link from console to organ. Thereafter it may convert to pneumatic action.

It is not unusual to find a mixture of all three types of transmission in the one organ. The difficulty arises where one type has been used extensively and/or in an inappropriate manner. Fashion is largely responsible for this.


This is the biggest subject. There are four basic families of pipe — flues, flutes, reeds and strings. The flues constitute the traditional organ sound, and are the only sound specific to the pipe organ. Materials used are timber and metal. Usually one section of pipework is housed in a box (the “swell box”), not unlike a giant dog kennel. The front of this box has shutters made of 2”- thick boards, and these pivot like Venetian blinds (at the organist’s command), and so control the amount of sound being let out. Again, the means by which this is done may be mechanical, pneumatic or electrical.

Timber pipes can suffer from woodworm, splitting (mostly at glue joints) and warping. Sometimes they have leather parts that rot. Metal parts can suffer metal fatigue.
The larger pipes can collapse on themselves due to their weight when they are not well supported. This can be hastened with higher temperatures in which we now tend to keep our buildings.

Unfortunately though, the most damaging element to pipework in people — tradesmen. Without realising, when working overhead or inside the organ, they can do untold damage. It is always wise to ask an organ builder what precautions should be taken prior to having work carried out in the general area of the organ. Having issued the relevant warning about “people”. I would at this point like to dispel the myth that visiting organists might damage the organ or whatever. This is a view taken up by some organists, who seemingly do not wish to have others use the organ, for whatever reason! Visiting organists using the instrument in a reasonable manner, will only benefit an instrument.

This brief outline of organs is intended only to act as an introduction to the subject. I am well aware that it is slightly sporadic, a necessary evil, given the many facets involved. Volumes upon volumes have been written on the subject by more learned people than I. However, this should at least encourage an appreciation for the pipe organ, and what is involved.

A good pipe organ will last indefinitely if given reasonable care. I recently inspected one dating from the 1740s, and with some work, it will play again. That puts some perspective on the subject. The 1740s of course is not typical here of course. The average pipe organ in Ireland is about 100 years old, and many of these are of very fine quality. It is important to treat them with the respect that you would give to a similarly-aged piece of furniture or whatever. Alterations, additions and changes must only be done with much thought, as the original historical value and integrity may be lost for ever. In short, just give them some respect.