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History Of The Pipe Organ

Construction Of The Pipe Organ

There are many aspects to playing the organ, from the moment a key or pedal is depressed, through the mechanisms, to the point at which the note speaks. The basic primary elements of a pipe organ are: “console”, (from where the organist conducts the functioning of the instrument, and where the manuals, pedalboard, and stops are situated); and “pipes”, (vertically-standing tubular structures which produce the sound).

Modern organs usually include more than one manual played by the hands, and a large keyboard played by the feet, called a “pedalboard”. The most commonly-seen configuration is two manuals, (the lower called the great, and the upper called the swell), and a pedalboard, with an additional pedal, called the swell pedal, (or swell box), which controls the volume of the swell manual when activated by the organist. Large organs can feature up to five manuals, although some of the largest have even more than this. Each standard keyboard commonly features five full octaves of notes, (or 61 keys); and a standard pedalboard commonly features two and a half octaves of notes, (or 32 pedals), however, there are variations depending on the period at which the instrument was built, and the location of its installation.

The pipes are placed on a “windchest”, which stores air under mechanically-produced pressure, (otherwise referred to as wind). Access of the air to the pipes is controlled by the activation of keys and pedals, via a series of leavers and shutters. Because of its constant wind supply, the organ is capable of sustaining sound for as long as the key is depressed, in contrast to other keyboard instruments, such as the piano and harpsichord, whose sound diminishes immediately after the key is depressed.

Organ pipes are arranged in sets, collectively called “ranks”. A rank is a complete set of pipes of similar timbre, tuned to a chromatic, (or semitone), scale. The great majority of ranks are mounted vertically, although some ranks may be mounted horizontally, as is the case with trumpet stops. The windchest is situated at the base of the pipes, which, when activated, stores a constant lung of air, which then breathes up into the pipes as requested by the organist. The manner in which the wind is admitted to the pipes varies, depending on the type of action, but in any case, several ranks of pipes may be supplied by a single windchest. A few of the larger pipes may be "off chest", in order to better fit them into the available space, or in order to feature them in the façade.

Pipes may be classified in several ways, each of which results in a different timbre: by the material they are made of, (wood or metal); by the mechanism of sound production, (flute or reed, also called labial and lingual); by the shape of the pipe, (cylindrical, conical, or irregular); and by the construction of the ends, (open or closed). A single pipe features: a “foot”, a column of differing lengths, which channels the air from the windchest to the pipe; a “belly”, the main body of the pipe; a “mouth”, where the sound speaks from; a “wedge”, where the air cuts onto and divides, producing the sound; and a “stopper”, a device at the top of the pipe used for tuning purposes. There are two main types of pipe used: flute pipes, which work in a similar manner to that of a recorder; and reed pipes, which contain a beating reed, working in a similar manner to that of a clarinet.

Because a pipe produces only one pitch at a time, ideally there is at least one pipe for each controlling key or pedal, although in some instances, one key may control more than one pipe at a time, such as a mixture, (a combination stop, consisting of several ranks of different pitches sounding together). The sound of a pipe can also be altered by use of a device called a Tremulant, which fluctuates the air supply going to the pipes, causing a tremolo effect.

The organ's individual ranks are activated by the organist, through the stop mechanism. There are many different varieties of stop mechanisms, some proprietary, but the principal distinction is between mechanical and electric. Mechanical stop mechanisms connect the stop controls directly to the windchest, through a series of wooden or metal rods. When the organist moves a stop control, the rods move, which activates the mechanism at the windchest, which allows or denies wind to the stop. Similarly, electric stop mechanisms control the mechanism at the windchest, through electromagnets.

Once a stop has been drawn, (the action of engaging the stop, either by pulling the draw stop out, or by rocking the tab switch), there is wind access to the ranks, controlled by that stop. Sound is then made by pressing down keys, which allows the wind to travel into each individual pipe. When multiple stops are drawn, the depressed key allows air to enter every rank that has been selected.

The choice of stop mechanism depends on the design of the organ, and the console. If the console is located further away from the rest of the organ, a mechanical action is harder to implement, than when the console and the organ are in closer proximity. The more complicated registration aids, such as thumb and toe pistons, (buttons located under the keyboards, and above the pedals, which allow combinations of stops to be selected without removing the hands from the keys), especially those which can be specified to control certain stops, require an electronic action, although a rudimentary system is available, with a mechanical action.

The stops on an organ, are the origin of the phrase, "to pull out all the stops", meaning to make every effort to make as much noise as is possible. However, as well as being capable of producing thunderous noise, the organ also delights in producing very delicate and beautiful sounds.