First Methodist Church,

Pitch Levels

Pitch Nomenclature | Pitch and Stop Names | Compound Stops | Tuning and Célestes


The pitch range of the organ is unusually wide for a single instrument. Organs have been built with pipes that sound as low as the C two octaves below that of the lowest C on a piano keyboard, sounding lower than human ear can hear. At the other extreme, pipes sounding to the top range of the piano keyboard are not unusual, giving the organ a pitch range wider than that of a symphony orchestra.

Referring to pitches within this wide range can pose problems in communication, both in terms of the organ and in broader musical contexts. A soprano, for example, will have a concept of "low B" that is markedly different from the specific B in the mind of a bassoonist when he or she hears the same term. Where only one instrument or performer is involved, there may be no problem in discussing, for example, a specific C. A pianist knows what "middle c" sounds like, and he or she can expect to hear that specific c when the correct key is played. On the organ, however, playing the "middle c" key can sound the expected c, the c an octave lower, or the one an octave higher, an octave above that, or even a g or an e. "Low C" on one stop might sound in a register that is different from that of "low C" on another.

The problem of discussing the pitch of organ stops is compounded by the way in which these pitch references are made. For organists, the usual method is to mention the pitch level of a stop in a way that is unique to the instrument - - to say that a given stop is of "4' pitch," for example. If the full system of pitch references is understood, that statement has some meaning. But if the system is not understood, the statement means nothing. The possibility for confusion is multiplied by the fact that this system of pitch references is based on the physical length of an open pipe sounded by the lowest C of a standard keyboard, but, in fact, in the case of any given stop, it may not really mean that the first pipe in a rank is actually four feet long.

To avoid the confusion presented by these vague but common pitch references, it is necessary first to understand a specific system of pitch reference that applies to all musical sounds, whether produced on the organ or by another musical instrument. There are several such systems, used within the contexts of both musical instruction and organ building in the United States, that seek to describe what octave range a specific note falls within. Because there are multiple systems in use, and they may at times be contradictory in the way they refer to the same pitch, they can actually add another level of confusion to the problem. As an example, consider this list of different ways of referring to the same pitch.

For the purposes of this tutorial, it is expected that a student will have some acquaintance with the system that is most commonly used in music instruction today. That system is explained below, and is used as a reference for the following discussion of pipes, stops and pitch. Other pitch reference systems, including those used by organ builders, are omitted from this tutorial.

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Pitch Nomenclature | Pitch and Stop Names | Compound Stops | Tuning and Célestes

Pitch Nomenclature

Music instruction in the United States commonly uses a system of pitch reference that divides the full range of audible pitches into octaves beginning on C's and continuing up through the next B. Because this system is the most widely used one in this country, it is adopted for use in this tutorial. Before this system can even be explained, however, some preliminary understanding of the range of organ keyboards and their relationship to the staff is necessary.

The range of the typical organ manual keyboard is 61 notes, encompassing five octaves as indicated on this diagram of a keyboard. 19 The third C from the lowest end is "middle c" and serves as the reference point for most organists as it does for pianists.

Diagram of 61-note Keyboard

Pedal keyboards typically have 32 notes in the United States, ranging from the same low C as the manuals to the G two octaves and a fifth above. The diagram indicates "middle c" on the pedalboard.

Diagram of 32-note

The staff below also shows the range of a 61-note manual keyboard as it is represented in notation. The most common system used in the US to describe pitch registers is included on the staff. 8 This system of pitch reference is then used in the discussion below of stops and pitches.

Great Staff with Octave

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Pitch Nomenclature | Pitch and Stop Names | Compound Stops | Tuning and Célestes

Pitches and Stop Names

The first system of pitch classification that an organist will encounter is that associated with stops, which are generally identified both with a name and with an arabic number. While the name indicates the timbre 52 of the sound, the number indicates the pitch of its lowest note. This is a system of pitch identification that is unique to the organ, and one that must be learned in order for an organist to fully understand the implications of the stop names of any organ. The arabic numeral found as a part of the name of most organ stops - - Piccolo 2', for example - - makes reference to pitch in a system that is physically based and unique to the organ. The most common number found is 8 or 8' and that pitch level can serve as the basis for an explanation.

On any stop, the Arabic numeral derives from the length of an open pipe that will sound when the stop is drawn and the lowest note on the keyboard is played. The pitch sounded is C, and all other pitches on that stop relate to that register, so that in effect drawing an 8' stop means that when middle c is played, the expected pitch (c' in the reference system) is heard. The rest of the 8' rank will consist of pipes that are progressively shorter, producing a chromatic scale for the 61 or 32 notes of the keyboard. An 8' stop can therefore be considered the normal pitch for organ stops.

If a 4' stop is drawn, and if that stop controls open pipes, the lowest key sounds a pipe that is one half the length and thus an octave higher. All pitches on that stop will also sound an octave higher, so that playing middle c actually sounds c". So long as the number associated with a stop name can be derived by multiplying or dividing the number 8 by a power of 2, the pitch sounded will always be the same. That is to say, playing a C key sounds a C pitch. A displacement by one or more octaves may take place, but the pitch will be the same.

Some stops, however, generally called mutations, will not sound the same pitch, but a different one. For example, a stop that includes 2 2/3 in its name will sound a g when the lowest C key is played. Such fractional numbers always produce pitches in the harmonic series, and the most common mutations will sound a twelfth above 8' pitch. This system of pitch reference in organ stops can be summarized in the following table, which gives the actual pitch sounded when middle C is played with the indicated stop drawn. In the table, clicking on the stop will bring up a file that sounds first middle C played on an 8' Principal (sounding c'), then the pitch sounded by a stop of the selected pitch level. For example, clicking on 4' plays middle C on an 8' Principal (c'), then on a 4' Flute (c").

For PC Users For Mac Users
32 C 3 1/5 e" 32 C 3 1/5 e"
16 c 2 2/3 g" 16 c 2 2/3 g"
10 2/3 g 2 c"' 10 2/3 g 2 c"'
8 c' 1 3/5 e"' 8 c' 1 3/5 e"'
5 1/3 g' 1 1/3 g"' 5 1/3 g' 1 1/3 g"'
4 c" 1 c"" 4 c" 1 c""

In some cases the pitch included in the stop name does not indicate the physical length of the lowest pipe, but of the sound of the lowest pipe. That is, if the sound of the lowest pipe in a stop is C, then that stop is labeled as an 8' stop. If that pipe is a stopped flute, however, the physical length of the pipe is only 4'. Similarly, the physical measurement of pipes of harmonic flutes, partially stopped flutes, and fractional and harmonic resonator reeds may differ from the pitch level indicated by the stop name. The general rule is:

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Pitch Nomenclature | Pitch and Stop Names | Compound Stops | Tuning and Célestes

Compound Stops

Compound stops often have no pitch indication as a part of their names. Instead, a Roman numeral indicates the number of pipes that will sound when a single key is played. Some organ builders will give both a Roman numeral indicating the number of pipes that play with each key, and an Arabic numeral indicating the lowest sounding pitch in that stop. For example, a "2 Plein Jeu V" would sound five pipes, and the lowest tone heard on that stop would be a 2' stop - - one sounding two octaves higher than normal pitch. Most compound stops include pitches corresponding to the fundamental and overtones of the harmonic series, but not all compound stops include all possible pitches. A special type of compound stop, the céleste, does not have any pipes that sound overtones of the fundamental. It is described in a separate section.


The Cornet usually sounds five pitches corresponding to the fundamental and first four overtones of the harmonic series. The table below lists the pitches sounded by the five stops of a Cornet V when the C an octave above low C key is played. In the interest of clarification, the table lists for each of the five sounding pipes the pitch both in two ways:

Stop Pitch8'4'2 2/3'2'1 3/5'
Sounding Pitchcc'g'c"e"

This recorded example demonstrates the composition of a Cornet V by introducing the pitches in succession. The fundamental pitch in this example is c, as in the table above, and the four additional ranks are added to the first stop (8') so that the recording ends with all five pipes sounding.

When five stops corresponding to those of the Cornet V are added one at a time, as in the recording above, or when a key in the lower register of the keyboard is played, the component pitches of the Cornet can be heard as separate pitches. Because the individual stops follow the overtone series, however, in the middle and upper range of the manual keyboard, where the Cornet is usually found, the upper pitches reinforce overtones of the fundamental of the lowest sounding pitch. As a result, the ear hears a single pitch with a rich overtone component, not five separate pitches. Therefore, although most Cornets use flutes as their individual pipes, the timbre of a Cornet is closer to that of a Trumpet than to that of a Flute because the ear hears the composite result of the combined overtones, not the individual ones.

The characteristic sound of a Cornet V in the upper register of the keyboard is demonstrated in a short recording.

Some Cornet stops may sound more than five pitches, others less. A Cornet VII, for example, will continue adding pitches of the overtone series to the list given above. When a Cornet has fewer than five pipes for each key, it is usually the 8' and 4' stops that are omitted. In such cases, for example, when a Cornet III is used, it is necessary to draw the Cornet with both an 8' and a 4' stop in order to hear the full sound of a complete Cornet V.


The Sesquialtera (also Sesquialter or Sexquialter) is a compound stop sounding two pipes of 2 2/3' and 1 3/5' pitches. Usually, the Sesquialtera is combined with an 8' stop, resulting in a sound that can resemble that of a Clarinet in some pitch ranges. Because of the reduced number of pipes, the Sesquialtera II lacks some of the strength of a Cornet V, although the sounds can be somewhat similar in extreme high ranges. A Sesquialtera usually has pipes that are narrower in scale than those of a Cornet, pipes that are in fact often of principal tone. The Sesquialtera can in those cases be used as an ensemble stop and combined with other principals to good effect.

Chorus Mixtures

Aside from the Cornet, the Sesquialtera, and some less common related stops, other compound stops are meant to be used in an ensemble. These are commonly referred to as mixtures, and there are several common names which are used for these stops. In addition to Mixture, which can be the name of a specific stop as well as the general term for this class of stops, these names are among the most common:

Generally speaking, chorus mixtures have several specific characteristics in common.

The structure of a typical Fourniture IV can be analyzed to demonstrate these common characteristics. The usual method of presenting the structure of a mixture is with a table that shows the pitches of each rank of the mixture throughout the full range of the keyboard.

11 1/3'2'2 2/3'4'5 1/3'8'
21'1 1/3'2'2 2/3'4'5 1/3'
31/3'1'1 1/3'2'2 2/3'4'
41/2'1/3'1'1 1/3'2'2 2/3'

According to this table, when the C key is played, four pitches sound in the Fourniture:

These pitch relationships are consistent through the first octave of the Fourniture, but at d the pitches drop one level to those shown in the third column. Again at d' there is another break, and even lower pitches are sounded by the four pipes of the mixture associated with each key of the middle octave of the manual keyboard. The table shows additional breaks occurring on both a', a" and e"'. At each point, lower pitches are sounded by the four pipes associated with any key.

The breaks can be heard in this recording of a C-major scale played through three octaves on a Fourniture IV alone. The scale begins on the lowest C of the keyboard and ascends diatonically for three octaves. The first three breaks indicated by the table above can be heard in the recording as the mixture introduces lower pitches at each point. In order to hear the breaks clearly, it will be helpful to play the scale mentally as the recording sounds, and to listen for a change in pitch as the keys d, d', and a' are played.

An alternate way of indicating the same structure is to show the interval above the fundamental instead of the stop pitch of each pipe. Therefore, an analysis of the same Fourniture could also be given in this way:


In reading mixture analysis tables of this type, the pitches at C would be interpreted as

The interpretation shows that the pitches indicated are identical to those represented in the first table. In published studies of organ design and construction, the two types of representation are used almost equally, with some authors simply preferring one system over the other.

Chorus mixtures are not meant to be used alone, however, in the manner demonstrated above. Instead, they are used as a part of an ensemble, typically being used in combination with unison and octave-sounding stops of principal timbre. An ensemble or combination of principal stops might include the following.

In such combinations, the individual stops are voiced so that the higher sounding pitches are not heard as independent pitches. Instead, the ear interprets them as overtones of the primary pitch being played, so that a more brilliant sound is heard. In a well-balanced ensemble of stops in this kind of combination, the primary pitch being played - - the pitch sounded by the 8' stop - - is never obscured, and the presence of overtone-sounding pipes serves only to reinforce it.

In such ensembles, the breaks allow a chorus mixture to add brilliance to the lower registers by sounding higher overtones of the primary (8') pitch being played. The lower pitches played in the upper registers prevent a mixture from playing pitches that are too high to hear, or that call for pipes that are too small to either produce or voice. More importantly, the lower pitches present in these registers of chorus mixtures strengthen a potentially weaker portion of the range of the primary stops.

The tonal properties of a chorus mixture are demonstrated in a recording of a C-major scale played for four octaves, first on a Fourniture IV alone, then on a combination of an 8' Montre, 4' Prestant, 2' Doublette and the same Fourniture IV

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Pitch Nomenclature | Pitch and Stop Names | Compound Stops | Tuning and Célestes

Tuning and Célestes

The sheer number of pipes in large organ can create problems in tuning. If several stops are drawn, playing a note on which one pipe is out of tune can be a distraction. The out of tune pipe causes a wavering or undulation in the sound when it is played with other pipes that are in tune.

One class of stops, célestes, intentionally uses out of tune pipes to create a special effect. Generally, in a céleste an entire rank of pipes is tuned slightly sharp, so that when it is played with a similar rank of pipes that are in tune, the wavering quality of sound is present on all notes. In some cases, the céleste rank is tuned slightly flat, with a similar result.

The sound of a string céleste is demonstrated in a recording that plays a short passage twice, first on an 8' Viole de gambe alone, then on the same 8' Viole with a Voix céleste added

In order for a céleste stop to work properly, it must be drawn with another rank of similar timbre. Often there will be a slight difference in tone color, created by some modification in details of construction, but the difference must not be so great that a totally different timbre results. Because of this requirement for similar timbres, célestes are rarely used in combinations of large numbers of stops, and their use is somewhat limited. On organs in the United States, célestes are most common using stops of string timbre, but flute célestes and even principal célestes can also be found.

The names of céleste stops usually include some reference to the primary stop with which they are intended to be used, and in most cases a word that indicates its céleste function is also present. Some stops actually draw both a unison (in tune) rank and the céleste rank, and in these cases the stop actually belongs to a special class of compound stops in which no overtone-sounding ranks are present. Some of the common stop names associated with céleste ranks are

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Pitch Nomenclature | Pitch and Stop Names | Compound Stops | Tuning and Célestes

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© 1998, James H. Cook