We left off near the end of my discussion of pipe work. Flue and reed pipes, stops and sliders, pallets and windchests. See Part 1 as needed, also the Havinga video.

One last tidbit, pipes can be encased in a box with shutters at the front, and sometimes also on the top. These shutters can be gradually opened or closed by a foot pedal centered above the pedalboard, one per swell box. You can see a set of swell shutters above the central V in the lower set of pipes in the above image.  Swell boxes provide some amount of crescendo/decrescendo capability, along with some corresponding increase/decrease in the upper harmonics. A gentle sort of muffling if you will. Most organs have at least one division (keyboard) under swell expression. Here, a 4 manual and pedal console with 3 swell pedals, many stop knobs, and multiple thumb and foot pistons for combinations (not covered herein).

 

 

So how on earth is all this controlled, behind the stop knobs, keyboards and pedalboard? The typical 61 note keyboard is roughly 33″ wide. The typical, insofar as there is such a thing, windchest is more than 8 feet wide.

There is a direct mechanical connection (the only option prior to electricity, or fancy but initially difficult games with pneumatics), between key and pallet, the ‘valve’ that lets air flow from the windchest to the pipes whose stops have been drawn. It’s complex, but needs to be sturdy and reliable. Fortunately, far fewer stop mechanisms are needed than keyboard mechanisms.

Tracker action is so called because the straight line links from the key are called trackers. If the key is hinged at the rear, behind the sharps/flats, the key is suspended, through all the linkages, by the spring holding the pallet closed. This is called, naturally enough, ‘suspended action’ and for some of us aficionados, it is the gold standard in actions. Note that pedals are hinged at the rear, despite ‘rear’ being reversed from the keyboards, that is, as far from the sharps/flats as the length of the pedal.

An aside on pedalboards. The American (AGO, American Guild of Organists) standard has the pedals radiating and concave, to more naturally follow the motion of the feet. The British (RCO, Royal College of Organists) are non-radiating/straight but are concave. The original European tradition is both non-radiating and flat. Again, see the Havinga video for an older European pedalboard. Clearly, the performance enhancements of radiating or radiating/concave may be real, but are relatively minor. Experienced organists claim switching between them is fairly easy.

Organists wear shoes with moderate heels to facilitate heel and toe playing.

When the key or pedal is depressed, the tracker is pulled down and the motion is transferred to the pallet. If the key is hinged in the middle, the tracker is at the rear of the key and is pushed up. It needs to be converted to a downward pull, which is accomplished by a backfall. Imagine a triangle with a pivot at its low apex, long edge on top and horizontal, the tracker pushing up on one corner, causing the opposite corner to move down:

But how to handle the disparity of width between keyboard/pedalboard and windchest? This is done with rollers, narrow but stiff cylinders with links at each end and able to roll around their horizontal center.  A downward pull at one end becomes a downward pull at the opposite end, pulling down whatever is above.

The final piece of the action (heh) is the square. A single square changes the direction of motion of the tracker, typically from a downward pull to a horizontal pull. A second square can then change the direction from a horizontal pull to a downward pull.  With rollers and squares, actions can be routed around corners.

Fuller details can be found at my source for the gifs linked above.

Trackers, rollers and squares make up ‘suspended action’, wherein the key is hung in place, suspended from, the pallet spring.  The first portion of a pedalboard tracker action:

 

From Wikipedia, Tracker Action

 

Now you have this set of parts for each of the (up to) 61 keys and (up to) 32 pedals.  The mechanism needs to be responsive, light in touch at the keys, adjustable in fine increments, and must all fit within the console and the space between it and the windchests.  No wonder consoles were/are so often embedded within the body of the organ:

 

 

Oops. What about the pipes that make up the facade? And the Trumpets en Chamade? Conveyances are used, tubes that sit in the windchest where the pipe would ordinarily go and are routed to the foot of the pipe in the facade. If the Trumpets en Chamade are on higher wind pressure than the rest of the pipes in their division, they may be on their own windchests, thus requiring yet more routing within the action. The same for other ‘high pressure’ ranks.

Prior to electric blowers, wind was provided by reservoirs fed by bellows pumped manually. Wind pressure ranges from under 1″ to 10″ or more, although 3/4″ to 5″ seems to cover the common cases. Wind pressure is measured by a water gauge, placed in a toe board where a pipe will go, with the water in a U-shaped tube.

I have not covered manual to manual or manual to pedal coupling, combination pistons (buttons seen below the keyboards and the toe studs seen above the pedal board in modern organs), nor electric, electro-pneumatic, nor pneumatic actions, or other details., but those quickly get into ‘eyes glaze over’ territory.

I hope you’ve gained some appreciation for the complexity of the organ and the skill and ingenuity of builders in the 17th through mid-19th century. That’s roughly when other action schemes began to come into play, some more robust and successful than others, but none with the sensitivity of the direct physical connection from performer to pipe of the tracker action. Tracker action began to make a serious comeback in the early mid 20th century, along with other traditional organ building techniques. Tracker action instruments are widely available today from the top builders in the world.

Thank you for reading!