Samford University, Beeson Chapel, LeTourneau Organ

Introduction

Windchests (usually referred to by the shorter form "chests") store the wind that is used to generate sound from pipes. Most chests are rectangular wooden boxes, eight or nine feet in length and varying form twelve inches to more than six feet in width. Usually a chest is no more than twelve or eighteen inches deep, but one form, the "Universal Air Chest"tm made by the Austin Organ Company, can be made as deep as seven or eight feet.

The top surface of a chest is the toe board, which has holes drilled through it to allow wind from the chest to enter the pipes. Ranks of pipes are placed on top of the chests, supported with a system of racks, and their toeholes line up with the holes in the windchest.

The actual working part of a chest is hidden from view, and it may take any one of several different forms. Although several different types of chests and associated actions can be found on organs the world over, there are three primary types of chests and actions which are commonly found on US organs today:

As you begin to pay more and more attention to written descriptions of pipe organs, you will soon run into some abbreviations that are potentially confusing: EP, ES, M, and a number of others. These are intended to be descriptions of an organ's "action," and it will help if you think of these as short cuts, not precise descriptions.

As you'll find out in the discussion below, your confusion stems from a conventional set of assumptions, and you haven't been initiated into their subtleties. You see, in the usual method, the term “action” is used in two separate and potentially confusing ways,

  1. At times, "action" describes or implies internal mechanics of windchest construction and design.
  2. At other times, the same word describes or implies the nature of the connection between key (or stop control) and chest.

Slider chests

As the oldest type of windchest that is in common use, the pallet and slider chest should present the clearest case. You might think so, at least, but in fact, it's sometimes the most confusing. Not only can the chest itself be built differently, but its sliders and pallets can be moved in different ways. The connection between chest and key can be mechanical, it can be a pneumatically assisted mechanical connection, or it can be an electrical connection. The builder makes choices, and in effect, the permutations of mixing different specific sub-types of slider chests with different types of connections have all been tried.

Let's look at the way a slider chest is built, first.

I shouldn't have to remind you, but there's a link on the left to a page that describes the Pallet and Slider Chest in detail. If some of the terms used here confuse you, look at the other page and then come back here.

When a slider chest is built in the centuries-old way, the pallets can be moved in the traditional manner — a plain old-fashioned direct mechanical link to the key. (That's described in the other pages of this tutorial as well.)

In the next slider chest you run into, though, the pallets might be moved through a pneumatically assisted connection, as in actions that employ Barker levers. (To see what that looks like, you'll have to visit the historical section of this tutorial; check out organs in nineteenth-century France.) For now, just trust me — the chests are the same, but the direct link is augmented by little pneumatic bellows. Trackers still go from the key to the Barker levers, and from the Barker levers to the windchest. The chest is built in the usual way, with wooden pallets, and you can still see trackers entering the pallot box. They've just taken a detour on the way from the keyboard.

In still another organ, you might find an electrical connection from the key that fires an electro-magnet that opens a pneumatic valve that moves the tracker that pulls down the pallet of a traditionally built slider chest. That might sound like a lot of trouble to go to between the key and the chest, but such things can be found. A row of "pull-downs" or trackers still enters the pallet box, but in this case they're very short. Instead of continuing through a serieis of rollers and squares to the keyboard, they go just a short distance to a row of pneumatic valves. In fact, the pneumatics are usually attached directly to the pallet box. Only an electric cable leads from there to the keyboard.

Here's the important point: In either case, the chest is built the same way. The difference is found in the connection between the chest at one end of the action and you — pressing the key — at the other. The chest is the same each time.

So far, I've only talked about the pallets and how motion at the keyboard is translated into allowing air into the key channels from the pallet box. Above the pallet box, there are also different ways in which the sliders can be moved: by a mechanical, pneumatically assisted mechanical, pneumatic, electro-pneumatic, or electrical connection from stop control to slider. In fact, there's an option here that you're just not going to find in the description of key actions: the mechanical connection with optional electrical connection or assist. Such duplication may be found in the couplers – yet another component of the action – but not in the connection between key and pallet.

In each of these examples, the construction of the chest is the same, but the connection between key or stop and the operative components of the chest is different.

By now you should be asking, "What does all of this have to do with EP, EM, M, and all the other possibilities?" I don't want you to lose track of where we're going on this page.

A "normal," traditional slider chest is usually assumed when we talk about "tracker organs," or "mechanical action." In fact, that's what the single M means when you see that abbreviation used; it stands for mechanical action, and such organs almost without exception in today's world are built with slider chests. The usual thing to do, though, is to describe the nature of the connection between chest and key or stop and imply the type of chest. Sometime you'll see the action of an organ described as having "mechanical key and stop action," or "mechanical key action and electric stop action." That's the way our organ works in the Recital Hall. Whenever you read this, you can assume — quite securely, in fact — that the windchests of that instrument are slider chests. Again, this terminology describes the connections and implies the type of chest -- a traditional slider and pallet windchest.

Electric Slider Chests

Sometimes you'll see the abbreviation ES, which stands for "Electric Slider" chest, but to complicate matters a little more, that doesn't even mean the same thing each time you see it. In most cases, it means that the traditional pallet -- the wooden wedge that lets wind into the key channels -- isn't there; it's been replaced by an electro-magnet that operates a lever that has a pad on the end (called a pallet, just to donfuse you even more). When the magnet fires, it moves the lever with its pad away from an opening into a key channel. This is different from the type of action described above, because this time the chest isn't built the same way; the traditional wooden wedge is gone. You don't see connections of any kind lined up and entering the pallet box in nice neat rows on this kind of organ -- just an electric cable.

In another type of ES chest, the Blackinton chest, the traditional pallets are replaced by rectangular pneumatic pallets. These pallets admit wind to the key channels by moving in a vertical direction, not at an angle, and they are activated by electro-magnets much like the ones used in electro-pneumatic windchests. In the Blackinton chest, though, they are inside of and actually form the working part of the pallet box. Just as in the case of a traditional slider chest with electric key action, there's an electrical connection to the keys themselves. This time, though, it is the chest that is different, not just its connection to the key.

One again, don't lose sight of the main point: "action" can mean windchest construction, the connection between windchest and key or stop, or even both. You have to understand what's implied as well as what's actually said when you read the abbreviation ES.

The usual term ES describes the chest and implies the connections. If you read about an organ with Blackinton chests, again, the chest is described, its connections implied. Quite the opposite of the situation in the preceding section.

Electro-mechanical Chests

The most common type of electro-mechanical action is Direct Electric Action, built by the Wicks Organ Company of Highland, Illinois. Other builders use a similar system, however, and in all of them, the usual descriptive term ("DE" for Direct Electric or "EM" for Electro-mechanical) refers to the way the chest is built. The connection between the key and the chest is, once again, an electrical cable.

The unusual thing about these windchests is their lack of a stop action. The operation that a true stop action usually performs is taken care of by a series of electrical relays, so that when you press middle c, for example, you don't get all the middle c pipes playing. But the relay is electrical, and so the connection between both key and stop control on one end and the chest at the other is electrical. (Well, today it may well be "electronic," and the cable could conceivably be replaced by a wireless connection, but at least there won't be a tracker or a Barker lever involved.)

This time, the usual description refers to the design and construction of the windchest. You wouldn't expect anything else with "electr" forming part of the name, of course, so the implied connection in DE or EM chests is an electrical one.

Electro-pneumatic Chests

The final description of an organ's action that you might find today is EP, which stands for "Electro-pneumatic." Once again, you'll be disappointed if you expect any consistency here. This time, though, the problem comes with the common practice of using a generic term to describe several quite different specific applications of the general principle. Here's a short list of what might be meant when you read about EP chests in an organ.

As you might expect, this list could be enlarged. At the same time, the connection from key or stop to the chest is similar, if not identical, in all organs that have electro-pneumatic chests: an electric circuit is closed and the signal transferred from key to chest through an electrical connection.

In the case of electro-pneumatic actions, then, the term describes the chest and implies the nature of the connections.

Other Types of Chests

Once you leave the sheltered walls of the College, you might actually run into some other types of action. I hope you have an experience with spring chests, for example, or that you discover what the touch is like with tubular-pneumatic action. While you are a student here, you will do well to notice the type of action you find on each organ you play. Each type of chest, and each separate type of connection between you and the chest, will affect not only your technique and what you do at the console, but also the music you make.

An organ's "action" -- whatever the term implies -- is important. Learn all you can about it.



© 1998 James H. Cook