The organ np

View from the Loft
This feature is an effort to let us as organists understand the noble instrument we play each day. I think the history of this instrument is fascinating so if there is an interest, I will give us a class in Organ History 101.

As the organ was developed through the years, the art of pipe manufacture was developed. This is really more of an art that a manufacturing process. Flue pipes are generally divided into three basic groups – principals, flutes and strings. There are no moving parts in flue pipes but each pipe contains several elements. First there is the main pipe body built to a specific length. On the upper end of the pipe is a tuning slide that lengthens or shortens the pipe. The bottom of the pipe is called the toe. This is the part that is placed into the wind chest. A tapered region at the bottom of the pipe is called the foot. Next comes a horizontal slit called the mouth. The beveled area below the mouth is called the lower lip and the area above the mouth is called the upper lip. Diapasons are made from a soft metal of tin and lead that is easily worked to form the pipe. As you may well imagine from this general description, there are many parameters that could be introduced to give the pipe a desired sound and volume. Each organ builder had his own tools and forms to build each pipe. In the case of an eight-foot pipe, this required building sixty-one pipes to include the entire range of the keyboard manual. Flute pipes are generally wider in diameter whereas strings are narrower.

Each pipe is based on the physical properties of a vibrating medium. Air is set into vibration when it strikes the mouth of the pipe. Air reacts the same way a taut string vibrates. As the string is plucked, it sets up a wave pattern based on its length and tension. The loudest vibration is the fundamental sound. It is the sound produced by the simple movement of the string between the two ends (nodes). There is, however, another vibration with a node at the center point of the string. This gives a secondary sound one octave above. So if the string is 8 feet in length, and the tension is set to sound a pitch at “C”, then the pitch set by the vibration at the midpoint (4-foot length) is an octave above. This tells us that a pipe at 4 feet in length will sound an octave above the 8-foot pipe. These basic laws of physics govern the building of organ pipes. Of course, the vibration of the string will also occur at one third the length giving a “g” pitch, and so on. The additional pitches are called overtones and they give the sound warmth by providing movement to the fundamental pitch.

To be continued…

By I. M. Dockay

This feature is an effort to let us as organists understand the noble
instrument we play each day. I think the history of this instrument is
fascinating so if there is an interest, I will give us a class in Organ
History 101.

Our trek through the historical development of the organ continues with the development of composition pedals and combination pistons. Up to this time, the organist had to set each stop individually to add or remove each rank of pipes. A change from a quiet peaceful hymn to a haughty anthem took some time and quite a bit of dexterity on the part of the musician to open and close numerous stops. The ability to make these multiple stop changes was simplified by the introduction of a set of small iron pedals that would open and close selected stops with a single action by the organist’s foot. These pedals mechanically cut down the air to certain sets of pipes or stops on selected soundboards. The group of stops actuated by any particular pedal was fixed and was made by the organ developer. The organist could not change the selection of stops.

An English organ builder Henri Willis who, after many years of testing and experimentation, introduced a pneumatic combination piston system that was a major improvement over the mechanical system. Each stop was fitted with a small bellows that, when expanded by compressed air, would open or close a stop. Pressing a small ivory or brass button admitted air to the bellows. (Small actuating pistons subsequently replaced the bellows.) The control buttons were small enough to be placed on a narrow strip of wood between the keyboards. Today this strip of wood is known as a piston rail. Having the piston buttons placed between the keyboards allowed the organist to activate the pistons or combinations with the thumb or any other available finger. Initially the pistons under a manual only controlled stops on that division but soon after “general” pistons were added that controlled stops on the whole instrument. In an interesting reversal, toes studs control pedal and some general combination stops. The development of the combination action system was no small addition. One cannot imagine the organ today without a system of pistons.

To be continued

By I. M. Dockay

View from the Loft

We talked about the development of the Choir or Positif organ in the last article. Another organ was being developed at about the same time. This was a small organ called an “Echo Organ”, a small organ in a limited space whose pipes were shut up in a box and placed a distance from the main instrument. All this was done to control the volume of the organ. Although a few Echo organs are still made today, they have generally been replaced by the Swell organ. The evolution of the Echo into the Swell organ was gradual but mainly through developments by English organ builders. In the year 1712 Abraham Jordan created an echo-box that had shutters which moved up and down like a window sash. As the shutters were opened, the volume of the organ “swelled”, hence the name of this type of organ. The shutters allowed the organist to control volume without the necessity of removing stops (pipes); hence, they kept the same total sound but at a selectable volume level. The shutters in this early box were opened by the organist’s foot using a very crude lever mechanism that took great effort. Imagine raising ten windows at one time. Often when the foot was removed from the pedal, the shutters fell down with a loud bang. This form of shutter was called a “nags-head” swell. The sash-shutter system was replaced by a set of overlapping shutters called a “Venetian” swell because of its similar appearance to a Venetian blind. This invention allowed the echo-box shutters to be opened and closed to many levels with very little effort by the organist.

The development of the pipes installed behind shutters gave the organ another degree of flexibility for use in a church service. Volume could be controlled and the organ could accompany a single voice, a small choir, or even raised to the volume level of the Great organ, giving the organist another range of sounds to embellish a hymn or anthem. As seen with the Choir organ, the Swell organ was easily incorporated into the organ manual by adding a third keyboard.

To be continued...

By I. M. Dockay