Description of our organ

Some information on Organs

with emphasis on the Sipe organ at First Presbyterian

Howard A. Smolleck, Organist

First Presbyterian Church

Las Cruces, NM

July 2005

 A little history

 Definition: For our purposes, an organ is a musical instrument in which sound is produced by air moving through tubes (“pipes”) or reeds. We shouldn’t refer to the console or keydesk (as it is sometimes called on a tracker instrument) as the organ. That’s just the “control center”. The “organ”, properly speaking, is what makes the sound, and much of it (at least the mechanism) is hidden from view in most organs.                                             

The organ is the oldest keyboard instrument. A Roman organ with 13 “keys” and 4 ranks of pipes, buried as a result of a building fire in about 250 AD, was unearthed in 1931and restored to playing condition. Later instruments were sometimes larger and had large keys or paddles that were struck with the fists, like a carilloneur (tower chime player) still does. Organs as we know them today, with keys like a piano, have been built for about 700 years. Surprisingly little change in the appearance of the keys has been made in 500 years, except for changing the number of keys or keyboards. It is almost surprising how similar the touch of the keyboard of a good organ of 1700 is to a good mechanical organ of today. Through many centuries, organ building was a specialized, constantly-evolving art which attracted some of the best technological and artistic talent. Skill in organ performance, also, was highly sought as royal courts, cathedrals and churches of all sizes, and even town halls installed organs and vied for performers.

 In contrast to the organ, the piano was invented about 400 years ago and reached its present form about 150 years ago. By the time the piano first appeared, keyboards as we know them had been in use for several centuries in organs, harpsichords, and other instruments.

 We should recognize that, until the Industrial Revolution, the pipe organ, as well as clockwork-like devices for playing organs and bells, represented probably the most complex and ingenious technical devices in human history. With modern improvements, and better scholarly research on historical instruments, the inner workings of a pipe organ are still intriguing. You can share in this by examining and listening to the First Presbyterian instrument.

Some information about the organ at First Presbyterian Church,

and about organs in general

 The organ at First Presbyterian is a mechanical (or “tracker”) instrument, in which pressing a key causes a series of levers, rods, rollers, etc. to move in order to open a valve which allows air into one or more pipes. This is the only instrument of its kind in Las Cruces (Only 2 other churches in the city have pipe organs, and they are both electropneumatic instruments, which use electric currents to open valves under the pipes. The First Presbyterian instrument uses electricity only for the stop action and to power the air blower.) The mechanism between the keys and pipes is similar to that used for centuries before the advent of electromagnets, which were first used in organs in the mid 19^th century.

 The typical modern American church or classical organ has several keyboards (“manuals”) of 61 keys each plus a 32-key pedalboard. The pedal keys look and function just like larger versions of the manual keys. On most American organs, like ours, the console is built close to American Guild of Organists standards. This involves a concave, radiating pedalboard instead of a straight one in which the pedal slats are parallel. Thus, as the legs are swung from left to right, the feet remain approximately the same distances from the pedal keys. The curvature of the standard pedalboard represents approximately an 8' circle in each direction.

 How does an organ differ from a piano or harpsichord?

An organ is primarily a wind instrument. Its sound arises from the action of air movement in metal or wood tubes (“pipes”). In contrast, a piano is a percussion instrument; sounds are produced when felt-covered hammers strike strings. Toy pianos often use wooden hammers that strike steel bars of different lengths. In a harpsichord, strings are plucked as the keys are depressed.

 Why doesn’t the organ have as many keys per manual (usually 61) as the piano (88)?

Very early keyboard instruments had keyboards that were limited to approximately the singing range of the human voice, plus perhaps a few keys. As musical needs developed, the ranges expanded. The organ has remained one of the most versatile of musical instruments. One reason is that different ranks of pipes can be combined at different pitch levels on the organ to cover a wide range of fundamental tones, far greater than that of the modern piano. We’ll explore that below.

 The piano as we know it today was developed long after the organ and harpsichord, and its range was expanded in the nineteenth century to be able to play music written in an increasingly extended range. The 88 keys on the typical modern piano allows playing of virtually all the piano repertoire. A few large grand pianos have more than 88 keys (usually 4 extra in the bass) but these are primarily for the purpose of including additional strings that sympathetically vibrate and add harmonics during the playing of higher-pitched notes. Conversely, some smaller and older pianos have fewer than 88 keys. Incidentally, the true name of the instrument is pianoforte which, of course, means “soft-loud” and refers to the wide range of expression possible through key touch.

 A few very large organs, such as the immense 7-manual instrument built for the Atlantic City Convention Center in the early 1930's, had nearly as many keys on each of the lower manuals as a piano does. One reason was that organs of this type often played transcriptions from other instrumental (or vocal) media, and sometimes electrically played an actual grand piano. Most organists and composers have not found it necessary to have more than three or four 61-key manuals and 32 pedals on an instrument. To play the wide range of organ literature now available, an instrument of three manuals is desirable.

 How many pipes does a typical organ have?

I’ve never counted them! But if I figure correctly, the First Presbyterian organ has

9 pedal ranks          x       32 pedals       = 288      

13 Swell ranks        x       61 keys       = 793

13 Great ranks        x       61 keys       = 793

            Total                           1874

 The total is likely a little smaller than this, since at least one of the mixture ranks does not have a complete keyboard compass.

 Organs have been built with more than 33,000 pipes, and very small ones can be effective with only two or three ranks (a couple of hundred or fewer pipes).

What is meant by such terms as “An 8-foot stop”?

One of the advantages of a large pipe organ is that stops can be combined at many different pitch levels. The basic pitch level of an organ is the 8-foot pitch(8'). It is called this because the “speaking length” of an open pipe required by the lowest (C) key or pedal on the typical modern organ (the C two lines below the bass-clef staff) must be about 8 feet if the “middle C” key is to sound the same fundamental frequency as “middle C” on the piano. The total actual length of a pipe is somewhat greater than the speaking length, primarily because of the length of its foot.

 What is the purpose of the pedal keyboard?

The pedal keyboard (or pedal klavier) is often used to play the bass, or lowest, voice required. Thus, in accompanying a hymn, the pedal will usually play the lowest voice line shown in the score. The basic pitch of the pedal is usually considered to be “16' ”, an octave below that of the manuals. However, the pedal division of a well-designed organ has an independent set of stops of its own and can thus play independent parts. In serious organ music, the pedal frequently carries the solo line or another important, distinct part. This ability of the pedal to play a separate voice line makes the organ somewhat unique among modern keyboard instruments (in times past, large harpsichords were frequently built with pedal keyboards, and some pianos were constructed that way as well).

 The First Presbyterian organ, like many small and mid-sized instruments, has two keyboards or manuals. Pipes of the upper keyboard (“swell”) are enclosed in a swell box which allows expression (changes in volume). Volume is controlled by means of a swell pedal, which resembles the gas pedal on an automobile. This pedal mechanically actuates a group of swell shutters in front of the swell box which open and close much like vertical blinds. (Volume is controlled this way because it cannot be controlled simply by changing the amount of air sent to the pipes; that would cause tuning problems). The swell pedal is said to be balanced, which means that it stays in whatever position it is left after the foot is removed, in contrast to many designs of a century and a half ago, in which the swell pedal had to be latched in specific positions. Large organs often have a crescendo pedal, similar in appearance, which .adds stops. As is typical with classical instruments, pipes of lower keyboard (“great”) and pedal on our instrument are unenclosed.

 Couplers allow the pipes associated with one manual to be played from keys on another manual or pedal. For example, the swell to great coupler enables any stops drawn on the swell (upper) manual to be played by the keys on the lower manual, while the swell to pedal coupler allows the pedal keys to play swell stops. Couplers allow sounds to be combined in very useful and interesting ways and effectively expand the capability of an instrument greatly.

 The harness

We’ll start our more detailed discussion on the pipe organ here, since this part of the organ is what interfaces between the performer and the actual sound-production equipment. The mechanism that conveys the performer’s movement of the keys to open the valves under the pipes is sometimes called the “harness”. In a mechanical instrument such as the one at First Presbyterian, the harness includes mechanical parts with names like trackers, stickers, backfalls,  squares or triangles, rollers and rollerboard, registers, register pins, guides, etc. You can see many of these by just opening the door to the organ chamber. The whole purpose of this equipment is to convey the performer’s instructions to the pipes. Although modern materials are used, the basic design of many of the parts of a mechanical organ has not changed in several centuries. We should point out that the mechanism of the organ is delicate and expensive, and is easily damaged even by inadvertent brushing against the exposed mechanical parts. Care must be taken by those privileged to have a  “backstage tour”.

 Most people realize that an organ has keys like a piano. It also has some means of selecting which groups (ranks) of pipes will be available, how the keyboards are coupled, etc. The devices on the keydesk that control these functions include what are sometimes referred to as stops (actually rocker switches on our instrument, and stop-tabs or drawknobs on others) and various other controls such as the combination-action buttons below the keys (which allow stops to be programmed in advance for quick recall). We will try to make clear what these things accomplish below.

 The wind supply and wind chest

The air supply to the pipes of an organ is traditionally called “wind”, which is of course under a slight pressure compared to the surrounding air. In our organ, it is supplied by a motor-driven blower and is at very low pressure (like blowing across a bottle lightly). The pressure in our organ is several “inches of water”. (To measure air pressure in an organ, water is placed in a transparent U-shaped tube, called a manometer or wind gauge, and one end is connected to the wind chest. The difference in the heights of the water columns is the wind pressure in “inches of water”.) All pipes on our organ operate at the same pressure, although the larger ones consume a considerably greater volume of  “wind”.

 Low pressures were needed when organs were pumped by hand, and there has been a return to low-pressure, traditional ranks in the mid twentieth century. Higher pressures provide louder sounds, while lower pressures generally result in a better tone. Large organs may have different wind pressures for different parts of the instrument. Some have much higher wind pressure, at least for some ranks, which usually makes those ranks much louder. Some ranks, particularly powerful reeds in large instruments, have been built to operate on as much as 100 inches of wind. These pipes provide spectacular fanfares.

 Originally, organs were pumped by hand or foot. In some instruments this required the constant exertions of several grown men to generate the volume of wind required. Sometimes these “pumpers” held on to an overhead rail while treading alternately on large bellows (the “treadmill”). This kind of arrangement had significant advantages for keeping the wind production steady, a problem which does not arise with the modern rotary blower.

 Pumpers began their pumping upon a signal from the organist, who pulled a bell cord or otherwise signaled the time to start. The necessity of hiring these pumpers meant that much practice was done on a silent organ or on large harpsichords which were fitted with pedal keyboards. As mentioned above, some pianos were even made with a pedal keyboard in the nineteenth century for this purpose.

 Electric motors began to take over the task of wind production in the nineteenth century. Even “water motors” (which used city water pressure to spin a turbine) were used widely a century ago to power the blower. Modern developments in electric motors (usually induction motors similar to the ones in evaporative coolers) have replaced nearly all these schemes in developed countries. Motor-driven blowers can operate for decades with virtually no maintenance. It is wise to filter the intake air.

 The equipment which supports the pipes is usually called a wind chest, although in England and elsewhere it is sometimes referred to as the “sound-board” (an unfortunate choice of word, because it does not directly affect sound production like the soundboard of a guitar or piano). A number of wind-chest designs have been used over the centuries. Two of the major historical types are the slider chest (and its relative, the spring chest) and the ventil. Of course, with the use of electric or pneumatic valves under each pipe, as in most electropneumatic organs, pipes may literally be positioned anywhere on a wind chest. (Acoustically, however, there are certain preferred schemes for positioning pipes relative to each other, since they interact with each other when several are sounded at once.) The First Presbyterian instrument uses the slider-chest principle.

 Just like steam engines, organ air systems have pressure regulators and emergency escape valves. The process of keeping a steady supply of air at constant pressure, regardless of how many keys are pressed or how many stops are drawn, has challenged the best designers over the centuries. Pipes of different types and pitches take drastically different amounts of air, but the pipes on a given wind chest must all operate at the same pressure. 

 The pipes: construction, voicing, tuning, and some other important concepts

 Primary types (or “families”) of organ pipes include:

? diapason or principal (the basic classical organ sound)

? flute

? string

? reed

 The first three of these families compose what are known as flue (or labial) pipes; they usually work somewhat like a recorder or whistle and include the designs we think of when we think of typical organ pipes. Reed or (lingual) pipes function differently; a reed pipe contains an actual vibrating reed. Pipes are usually made of some variety of wood (in which they typically have a rectangular or tapered rectangular or even triangular shape) or metal. Much discussion has taken place over the centuries concerning pipe materials. Most metal pipes are an alloy representing some combination of lead, zinc, and tin, although display pipes may be copper or some bright alloy. Recent studies on organ pipes of several centuries ago, in light of modern metallurgical technology, have shown that the manner of melting, casting, and cooling the pipe metal can have a significant effect on tone, and this explains why so many historical organs of several centuries ago seem to sound so good.

 Organ pipes are built in ranks (a rank is a group of pipes, usually spanning the complete keyboard or pedalboard, that look and sound similarly but at different pitches). Pipes in a rank must be appropriately scaled. This means that larger pipes are nearly replicas of smaller ones, becoming larger in diameter as the height is increased. The point at which the effective speaking length is half that of the largest one is an important specification. Often, for example, the scaling is chosen to reduce the diameter of the pipe in half at the 17^th key up the scale within in a rank. Pipe extremes are narrow-scale (producing string-like sounds rich in overtones, or harmonics) and wide-scale (producing flute-like sounds having few harmonics). Although the pitch of a pipe is primarily related to its length, width is a factor too; wide-scale pipes can be a little shorter than theory dictates.

 The First Presbyterian instrument has a total of 26 stops and 35 ranks of pipes. These ranks can be combined in various ways to provide particular effects at the desired volume.

 Once built, pipes must be voiced or finished, preferably in their final acoustic setting. Then they must be tuned. Voicing flue pipes primarily involves altering slightly the mouth of the pipe. By changing the cut-up, which is the vertical size of the mouth opening, one can change the type of sound to some extent. Nicking, or cutting small nicks in the edge of the horizontal languid or block at the base of the mouth, also changes the character of the sound and controls the amount of chiff, or initial wind sound characteristic of organ pipes. Builders and technicians have widely-different views on these issues. Reed pipes are voiced primarily by shaping (curving or thinning) the reed or tongue, which is usually brass. A reed pipe which is louder or softer than its fellows usually requires the reed to be removed and slightly straightened or curved.

 Periodic tuning and other routine maintenance is required. With hundreds of pipes, some the size of a pencil and very close together, tuning an organ even the size of the one in First Presbyterian is a major and delicate undertaking.

 Metal pipes are usually constructed of a soft alloy that allows the pipe to be manipulated for tuning purposes. Open metal pipes (such as the display pipes at First Presbyterian or St. Andrew’s) often have a tubular slide at the top as an extension of the pipe, for tuning, or a “roller” (resembling the pull-away top of a sardine can) that can be adjusted to change the pitch by changing the effective length of the vibrating air column. Some have a close-fitting collar that can be slid up and down to change the pitch, while some pipe tops are simple rims whose diameters need to be expanded or contracted for tuning. Widening the top of a pipe (called “coning out”) raises its pitch. Open wooden pipes have something analogous to these: a bendable “tuning shade” of metal on top of the pipe or a wooden slide on its side. Stopped pipes usually have a movable cap, or a stopper with a handle, at the top of the pipe. Especially in tuning small pipes, tools rather than the hand should be used, both to reduce the effects of temperature and to avoid getting nearby pipes out of tune. Reed pipes have a slider (usually a stiff piece of brass wire) that presses against the reed; it is moved up or down to tune the reed. Many of these tuning motions require delicate movement, often a hundredth of an inch or less.

 Doubling the length of a pipe lowers its basic pitch an octave (that is, it halves the frequency of vibration). Conversely, shortening the speaking length to half raises its pitch by an octave. One can use this principal to reduce the length (and thus the cost) of large pipes, but at the expense of the harmonics which the pipe will produce. Pipes at the low end of the keyboard can become really large and heavy, with one such pipe and its associated equipment costing almost as much as an entire rank of smaller pipes. Large pipes must be carefully supported or they can fall or even collapse on themselves over time.

 Effect of temperature and humidity on pitch

Pitch (the basic tone at which a pipe sounds) is affected by temperature and humidity. Metal pipes shrink as the temperature drops, and you would think that this would cause them to sound sharp, but the air column is much more effected by temperature than the metal, and this makes the sound of metal flue pipes go flat significantly as temperature drops. Wooden flue  pipes go flat as temperature drops like metal ones, but primarily in short (2 feet or less) pipes. Reed pipes go slightly sharp as temperature drops, because the reed shortens slightly with temperature. Thus, temperature changes can have a profound effect on tuning, resulting in the well-known advice to try to keep the temperature at the pipes fairly constant. Also, wood expands with moisture, possibly changing the pitch in wooden pipes. Builders have recognized these problems for centuries and have responded in many ways, such as trying to place most pipes on nearly the same level, recognizing that air in a building tends to stratify by temperature.

 It is not enough to keep the pipes at constant temperature to avoid out-of-tuneness. If the air forced through them is not at the same temperature as the pipes, tuning problems can result. Since many organs are large devices with pipe chests in several locations, with the blower in a different place, in reality all of the pipes are seldom in tune, even shortly after a professional tuning. 

 Thus, in order to keep a pipe organ in tune, it is wise to try to insulate it from major changes in the weather. For this reason, organ technicians recommend that the building be brought to normal temperature (and ideally to stable humidity) several days prior to tuning. With the new heating/cooling plant at First Presbyterian Church, the organ is now more stable with regard to pitch.

 ...and more details for those who want to really delve into how organ pipes work...

 Harmonics are sounds of higher frequencies than the fundamental, related as multiples of the fundamental frequency. For example, if the A key above middle C on a piano is sounded, a basic (fundamental) sound that vibrates at 440 cycles per second will be produced (This sound lies at about the middle of a typical woman’s voice range). However (and fortunately for us), other sounds will be produced by that string, including perhaps the second harmonic (at 880 cycles per second), the third harmonic (at 1320 cycles per second), and so on. It is these harmonics, of different amplitudes in different types of sounds, that give the tone its richness and character. Like strings, organ pipes generate harmonics, and specific pipe designs can aid or suppress particular harmonics.

 A pipe is said to be “open” when its top is uncovered. It is said to be closed or stopped when its top is covered. Stopping a pipe lowers its pitch by approximately an octave. This provides an obvious advantage in fitting an instrument into a small vertical space, as well as savings in material. However, a stopped pipe produces only odd harmonics, whereas an open pipe theoretically produces all harmonics. An organ builder can exploit this idea to make sounds of various character available.

 Pipe ranks are usually designated by a tonal name and by a number designating the speaking length of the longest pipe. The “Principal 8" rank on the Great, much of which forms the display pipes which you see in the chancel, is an example. This rank of open pipes produces a strong, basic organ sound, and is often called a “diapason”. It is this kind of sound and pipe appearance that most people think of when they think of a pipe organ. The longest pipe in that rank is about 8 feet in speaking length. The largest pipe of the Bourdon 16 rank on the Great is also about 8 feet, but this rank is stopped and thus produces sounds that are an octave below those of the corresponding members of the 8-foot ranks.

 Obviously, it follows that a 4' stop will produce a sound an octave higher than “concert pitch”, and a 2' stop will produce a sound 2 octaves higher.

 A rank which does not sound at unison pitch or one or more octaves above or below unison pitch is called a mutation. Our organ has one mutation stop, numbered 1 1/3. This stop, whose lowest pipe is about 1 1/3 feet in length, produces a sound two octaves and a fifth higher than the corresponding pipe on an 8' rank. Thus, with this stop drawn, if you press a C key, you hear a G sound two and a half octaves higher. Frequently, an organ will have a rank of pipes pitched at 2 2/3', which of course would produce sounds an octave lower than the 1 1/3' rank. (Since our organ does not have the frequently-needed 2 2/3' rank, we obtain it by drawing the 1 1/3 stop and playing an octave lower than written.) A large organ may have many mutation stops, usually at pitches sounding fifths and thirds.

 There is an easy way to tell whether a mutation will sound a fifth (“quint”) or a third (“tierce”). If the denominator of the fraction in the stop’s length is a 3, the pipe sounds a fifth. If the denominator is a 5, the pipe sounds a third. Another interesting fact can be observed by expanding the fraction. For instance, 2 2/3  = 8/3. This tells us that the rank is based upon an 8' pitch, and sounds the third harmonic of the key played.

On the other hand, a 1  3/5 (= 8/5) stop would sound the 5^th harmonic of an 8' rank, which for a C pipe would be an E two octaves and a major third above.

  (All of this is easy to understand if you remember that the first few harmonics of a sound, for a C pipe, are in the order C  C  G   C   E   G   Bflat   C ...) So most of the lower harmonics are octaves and fifths.).

 Mixtures are stops that include more than one rank. There are mixtures of 2, 3, and 4 ranks on this organ. By convention, mixture stops include a Roman numeral in their designation. A Mixture III designation, for example, indicates the presence of 3 ranks. That means that each key sounds 3 pipes when this stop is drawn. Unfortunately, the Roman number doesn’t tell you anything about what scale degrees the pipe actually sounds.

 Mixtures usually include mutation ranks. Their small pipes are usually high in pitch and add pungency and tone color to the ensemble. As they progress up the keyboard, mixture ranks usually “break back” periodically to avoid extremely small pipes whose sound cannot be heard by the typical human ear. The pipes in a mixture are usually tuned to octaves and fifths, or sometimes thirds. On a large organ, the name of a mixture stop may give a clue as to what ranks of pipes it contains as, for example, Cornet V or Sesquialtera II. Playing a single key with a 3- or 4-rank mixture stop on, as you can see, really sounds a chord in some cases, or at least several intervals.

 We have referred to three classes of flue pipes above: principal, flute, and string, and we already discussed the principal or diapason. Flute ranks have few upper partials and sound somewhat like actual flutes or recorders. Of course, a large organ will have several contrasting flute sounds, at different pitches. String ranks usually have very narrow scaling (i.e., these pipes are thin compared to their length) and produce sounds rich in upper partials, like the bowed violin string, hence their name. Flutes, by contrast, often have wider scaling. Complete books have been written concerning the many varieties of tone to be found in large organs and the typical names by which they are called. Hundreds of different ranks have been described and constructed, some extremely unusual in appearance or sound.

We have here been talking primarily about flue pipes, in which the sound is made in a manner similar to that of a tin whistle. In reed ranks, the sound is produce by a vibrating reed. The reed is close to the boot, or bottom, of the pipe. The tube above this, or resonator, can be shaped in various ways to control the timbre of the sound. Since it is the reed that produces the sound and primarily determines the pitch, the resonator can be made much shorter than the column required for a flue pipe. Thus you will see 16-foot reed stops whose longest pipe might be only 5 or 6 feet, as in our organ. Short resonators often lead to “buzzy” sounds; long resonators are more characteristic of orchestrally imitative sounds like the trumpet. The instrument at First Presbyterian has five reed stops: two on the swell, one on the great, and two in the pedal.

 A reed pipe is tuned primarily by adjusting the vibrating length of the reed. In practice, this is done by sliding a wire up and down. This wire impinges on the reed and controls its effective length.

 Reed stops are particularly susceptible to dust and other debris, which can easily fall down in the open (and often funnel-shaped) top of the pipe. If a reed pipe doesn’t speak, it is likely because of dust or other material near the reed. It could also be because the reed itself is not sufficiently curved. In practice, during voicing the reeds are placed on a wooden block and rubbed with a burnisher to induce a very slight curvature. Adding curvature increases the volume of the sound, but makes the speech of the pipe more uncertain. A reed that is absolutely straight would probably not speak, nor would one with too much curvature. Voicing is an art. 

 Reed stops are often considered to stylistically imitate brass instruments. They are found most frequently at unison pitch or an octave lower, or even sometimes an octave higher. Thus you may find a trompette 8 or hautbois (oboe) 8.  Such reed ranks are often used for solos, accompanied by flue ranks on the other manual or pedal. “Trumpet tunes”, with which the literature abounds, sound most appropriate when played on some reed stops, possibly with other ranks drawn as well. However, it should be remembered that the sounds of organ pipes are in reality distinctly different from those of other musical instruments, even though they may suggest other instruments.

 A very short primer on tuning systems

 Most keyboard instruments today are tuned to what is known as “equal temperament”.  To understand what this means, and its significance, we need to explore the topic in a little detail. The word temperament refers to the change made in tuning a note from what a “perfect” interval involving that note would sound like. Temperament systems, necessitated by the peculiarities of the acoustical physics involved, have been discussed for thousands of years. The Greeks recognized the problems involved about 600 BC, and the Chinese addressed these issues much earlier. The reason for so much discussion in this area is that, despite the apparent simplicity of the acoustical physics involved, natural tuning systems always theoretically introduce inconsistencies as we try to tune all of the keys even within the span of an octave.

 A perfect interval is one that has no beats. If you listen to the sound of two notes an octave apart on a freshly-tuned piano, you will be able to recognize that two tones are sounding simultaneously but you will hear one continuous sound with no beats. So a properly-tuned octave is always a perfect interval. However, if you sound the keys middle C and the F above it (a fourth) or C and G (a fifth), you will hear slow beats, like a tremulant. These beats are necessary in the equal-temperament system, where all intervals except octaves are adjusted from their “perfect” values. Equal temperament allows us to play in all major and minor keys equally well, and is thus necessary in order to be able to transpose from one key to any other of choice. Since the mid nineteenth century, when much piano literature in the style we know began to be written, equal temperament has become favored for keyboard instruments because of its versatility, allowing composers to write in any key and to move equally well among the others. The system, of course, is a compromise, and there are valid reasons for using other tuning systems. In reality, true equal-temperament tuning has probably only been possible since about the time of World War I. Prior to that, the tempering of most keyboard instruments was such as to favor some major and minor keys slightly. This is why we sometimes read paradoxical statements like “this piece sounds immeasurably better in E major than in C major”. Under true equal temperament, a piece played in whatever key would sound exactly as if played in any other key, just at lower or higher pitches.

 Even though we call the interval C-G a “perfect fifth” and the interval C-F a “perfect fourth”, we should recognize that, for an instrument tuned to equal temperament, these intervals are not “perfect” (= beatless). Near the middle of the keyboard, for instance, you can hear the slow beats if you listen. Almost anyone can hear these beats with a little practice. Other intervals, such as thirds and sixths, have considerably faster beats in equal temperament.

 Probably the easiest tuning system to understand is “just” temperament, in which (usually) the fourths and fifths are tuned with no beats. (The technical reason they can be tuned with no beats has to do with the fact that the ratios of the vibrational frequencies of the two notes in the interval are simple numbers: 2/1 for the octave, 3/2 for the perfect fifth, 4/3 for the perfect fourth, etc.) To tune just temperament, you might start by tuning C from a tuning fork, then the intervals C-G and C-F, which are tuned perfect. Then other fifths (G-D, D-A, etc.) are tuned, also beatless. The problem, once all the semitones are tuned in this manner, is that some major and minor chords sound really bad (lots of beats), and there will always be at least one fifth that is not perfect. I could explain it to you easily with a pencil and paper; it’s just the way the mathematics works!

 As keyboard instruments and the music for them evolved, tuning schemes were developed to make more chords sound acceptable. Various “meantone” schemes, which involved splitting the error and preserving beatless thirds and some fifths, were used. Unfortunately, as composers began to write more adventurously in other keys, more unpleasant-sounding intervals began to be used. Such tuning schemes were supplanted with “well-tempered” schemes. The famous sets of preludes and fughes by Bach, known as the Well-Tempered Klavier, which each contain a prelude and a fugue in every major and minor key, were written to exploit these systems. Contrary to popular belief, the tuning scheme involved was not equal temperament but well-temperament, a compromise that allows most (but not all) major and minor chords to sound acceptable. This was realized in recent times as experts noted that the compositions in the different keys were carefully written to exploit the subtle differences between the keys, not to show that the same piece in whatever key would sound alike (which as we said would be possible only in truly equal temperament, which most of our instruments approximate quite well today when done by a good tuner or electronic tuning aid).

 Since the character of playing in different keys can be emphasized by other tuning systems, some of the tuning systems popular when much of the organ literature was written (before the twentieth century) are finding fashion again. Some electronic organs allow the performer to tune the instrument to a choice of eight or so different schemes at the turn of a dial, allowing us to hear and compare these systems and revisit these issues that were debated so hotly in previous centuries..

Stoplist of Robert Sipe tracker organ at First Presbyterian Church

 Las Cruces, New Mexico

26 stops      35 ranks        Installed 1980

 In order of rocker tablets, left to right:

Pedal

Subbass 16

Octave 8

Spitzflöte 8

Choralbass 4

Mixture III

Fagott 16

Trompete 8

Great to Pedal

Swell to Pedal

Swell

Viole de gambe 8

Viole celeste 8

Rohrflöte 8                    

Principal 4

Nachthorn 4

Gemshorn 2

Quinte 1 1/3

Scharf III-IV

Basson 16

Hautbois 8

Tremulant

Great

Bourdon 16

Principal 8

Gedeckt 8

Octave 4

Spillflöte 4

Super octave 2

Sesquialtera II

Mixture IV

Trompete 8

Tremulant

Swell to Great

 There are 10 general settable presets, 5 of which (1-5) are duplicated as toe studs.

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