Organ stops explained: families, ranks, and how to read a stop list
An organ stop is far more than a knob on a console. Each drawknob, tablet, or piston controls an entire rank of pipes, and the combination of those ranks is what gives a pipe organ its voice. When a builder publishes a stop list, they are describing the instrument’s musical resources in shorthand, and learning to read that shorthand is the fastest way to understand what an organ can actually do. Whether you sit at the console, sing beside the organ in a choir loft, or simply want to know why one instrument sounds brighter than another, a working knowledge of organ stops pays back immediately.
This guide works outward from the single stop to the full instrument. It explains how stops are grouped into families, what rank and pitch level mean, how the same stop name can describe very different pipes on two organs, and what to look for when you read any stop list you meet. It also points to the wider educational resources on pipe organs maintained by Martin Ott, where the principles here are applied to specific instruments in the organ archive.
What an organ stop actually controls
Every organ stop, no matter how it is drawn or switched, opens a valve that lets wind reach a complete set of pipes called a rank. A rank usually contains one pipe for every key on the keyboard, though some ranks stop short at the top or bottom of the compass. When the stop is off, the pipes sit silent; when it is on, every pipe in the rank sounds when its key is pressed.
The pipe at the top of the keyboard may be a few centimeters long, while the lowest pipe of a 32-foot stop can stand taller than a person. Because each stop loads its own set of pipes onto the wind supply, pulling more stops makes the instrument work harder. That physical reality is one reason organ registration is a craft, not just a matter of taste.
The main organ stop families
Stops are grouped into families by how their pipes produce sound. The three great families are flues, reeds, and mixtures, and each behaves differently in music.
Flue pipes: principals, flutes, and strings
Flue pipes work like a whistle. Air splits against a sharp lip and the body of the pipe sets the pitch. Within the flue family, builders distinguish three broad groups by tone color.
- Principals are the chorus voices that define the sound of an organ. They are cylindrical, open, and relatively wide in scale, producing a round, singing tone with strong upper partials. The 8-foot Principal on the main manual is the backbone of most registration.
- Flutes use wider, often stopped or capped pipes with a softer attack. Names such as Flute Harmonique, Bourdon, Koppelflote, and Spitzflote describe different shapes and voicings, but the family character is gentle and even.
- Strings are narrow-scaled, sometimes stopped at the top, and designed to blend into a choir texture without covering other voices. Salicional, Viola da Gamba, and Voix Celeste are typical examples.
Reed pipes: trumpets, krummhorns, and regals
Reed pipes use a vibrating brass tongue called a reed against a curved metal boot, with a resonator that tunes the sound. They are the most colorful family and the most projecting. Trumpet, Posaune, Trompette, and Clairon are full-length chorus reeds, while Krummhorn, Vox Humana, and Regal are shorter, softer solo reeds with very different characters.
Mixtures and compound stops
A mixture is a single stop that sounds more than one pipe per key. Pressing middle C on a typical Mixture might bring in pipes at the octave, the twelfth, and the fifteenth above the keyed note, all at once. Mixtures add brilliance to choruses and define the sound of a strong principal chorus. Other compound stops include Cornet (a solo-tierce mixture), Sesquialtera, and Carillon.
Length, pitch, and the meaning of foot numbers
Every pipe organ stop is described by a number, a unit, and a name. The number and unit tell you the lowest pitch the stop will produce when a given key is pressed.
| Marking on stop | Sounds at written pitch | Typical role |
|---|---|---|
| 8′ | Unison with the keyboard | Foundation of chorus and solo work |
| 4′ | One octave above the keyboard | Adds brilliance, defines principal choruses |
| 2′ | Two octaves above | Sharpens the sound, used with mixtures |
| 16′ | One octave below | Weight and gravity, pedal foundation |
| 32′ | Two octaves below | Grave sub-bass, only in large instruments |
| 2 2/3′ | A twelfth above | Tierce ranks in mixtures and chorus work |
| 1 3/5′ | A seventeenth above | Seventeenth rank, brightens mixtures further |
The foot number is the length of the longest pipe in the rank, measured in feet. It is a rough guide to pitch, because pipe length is not the only factor that sets frequency, but it is the universal shorthand. Two stops both marked 8′ on different organs will be at unison pitch, but they can sound entirely different in color, scale, and voicing.
How to read a stop list
A stop list is a table that describes every rank on the instrument. It is usually arranged by manual and pedal, with columns for stop name, length, and sometimes the number of pipes. Once you know the conventions, any stop list becomes readable in a few minutes.
| Manual | Stop name | Length | Type | Notes |
|---|---|---|---|---|
| I Great | Principal | 16′ | Flue | Open metal, heavy scale, chorus bass |
| I Great | Octave | 8′ | Flue | Principal scaling, defines unison chorus |
| I Great | Super Octave | 4′ | Flue | Brilliance |
| I Great | Mixture IV | 2′ | Compound | Four ranks, breaks at tenor C |
| II Positiv | Salicional | 8′ | String | Narrow scale, solo or accompaniment |
| II Positiv | Cromorne | 8′ | Reed | Short resonators, capped reeds |
| Pedal | Subbass | 32′ | Flue | Stopped wood, resultants above |
| Pedal | Posaune | 16′ | Reed | Full-length, chorus reed |
A few rules of thumb help when you scan a list. Roman numerals after a stop name indicate the number of ranks in a mixture, so Mixture V is louder and brighter than Mixture III. Words such as gedeckt, bourdon, and coppel point to stopped wooden pipes, often warm and fundamental in tone. Words such as flute harmonique, principal, and montre usually mark open metal pipes of chorus grade. When a stop is marked ext. for extension, the lowest notes are produced by longer pipes borrowed from another rank rather than a full set of the named stop.
Couplers and how stops combine
Stops do not exist in isolation. A coupler connects one keyboard to another so the keys of the second manual also play the pipes of the first. When the Positiv is coupled to the Great, every Positiv stop becomes available on the Great manual as well. Couplers do not create new sounds, but they multiply the combinations, which is why a modest instrument with three manuals can still feel generous.
- Manual-to-manual couplers (Swell to Great, Positiv to Great, and so on) transfer stops up or down at unison unless marked sub or super.
- Pedal couplers link each manual to the pedal division, often at multiple pitch levels.
- Octave couplers (Super and Sub) shift the pitch of the played notes by an octave, useful for adding brilliance or weight without changing registration.
Because couplers do not change the pipes, they do not alter tone color, only the number of pipes sounding at once. This is why an organist can use a 4′ Principal coupled to the manual and still hear the character of the rank, not a new stop.
Chorus work: building a principal chorus
A principal chorus is the layered combination of unison and octave principals, a tierce rank, and a mixture, all from the same family. Building one is the clearest demonstration of how stops work together.
- Start with the 8′ Principal. Listen for the round, singing tone at the center of the keyboard.
- Add the 4′ Octave. The sound gains a second voice an octave higher and becomes more focused.
- Add the 2′ Super Octave. The line sharpens, and the top of the chorus starts to sparkle.
- Add a mixture (often Mixture IV or V). Each key now sounds several ranks at once, lifting the texture.
- Add a 16′ Principal in the bass if the manual has one, to ground the chorus in the lower octave.
- Add a reed such as a Trumpet 8′ to project above the chorus in a large space.
The order matters less than the balance. Each stop should add something the previous one did not, and the result should feel like a single instrument, not a stack of unrelated ranks. This is the central skill of registration, and it is what most builders mean when they say an organ choruses well.
Common stops and their typical use
The same names appear again and again in European and American building traditions, and while the sound varies, the role of each stop is fairly stable. The table below summarizes what a player usually expects when they see these names.
| Stop name | Family | Typical use |
|---|---|---|
| Bourdon 16′ | Flue (stopped) | Warm pedal foundation, soft solo |
| Flute Harmonique 8′ | Flue (open) | Solo melody, hymn accompaniment |
| Viola da Gamba 8′ | String | Color solo, expressive prelude registration |
| Salicional 8′ | String | Soft accompaniment, choir blends |
| Gemshorn 4′ | Flue (open narrow) | Flute solo, chorus filler |
| Tierce 1 3/5′ | Flue (small) | Adds tierce to mixtures and cornets |
| Trompette 8′ | Reed | Chorus reed, fanfare |
| Clairon 4′ | Reed | Bright pedal reed |
| Vox Humana 8′ | Reed | Solo ornament, expressive lines |
| Carillon | Compound | High mixture, often on a Positiv |
Stopped, open, and the geometry of pipes
Two pipes of the same length sound an octave apart if one is open and the other is stopped. This is why a stopped wooden 16′ stop has the same pitch as an open metal 8′ stop, and why builders use stopped pipes to keep the largest ranks inside the available space. The trade-off is a darker tone with fewer upper partials, which is why open metal is preferred for chorus principals and stopped wood is preferred for foundations and flutes.
Conical pipes, flared at the top, sit between stopped and open in character. They are used for many solo flutes and some reed resonators because they produce a fuller harmonic spectrum than a straight cylinder of the same length.
What a stop list does not tell you
A stop list names ranks, but it cannot describe the voicing that gives an organ its personality. Two instruments can both offer a 8′ Principal, a 4′ Octave, a Mixture IV, and a 16′ Posaune, and still sound very different. Scale, pipe material, wind pressure, voicing of the upper partials, case position, and room acoustics all shape the final result. This is why hearing an instrument, or studying a careful recording, always reveals more than the stop list alone.
For a player planning a recital or a congregation choosing an organ for a new build, the stop list is a starting point, not a verdict. The same stops, well voiced in a sympathetic room, can carry congregational singing and solo literature with equal ease. The same stops, poorly voiced in a dry hall, will sound thin no matter how elaborate the console.
Practical checks before you judge an organ by its stops
Whether you are a visiting organist, a singer, or a committee member, a few quick checks will tell you more than a long list of names.
- Read the stop list for the families you need. Look for at least one strong principal rank at 8′, a reed that projects, and a pedal division that can ground the sound.
- Ask about the wind supply. A well-built organ with steady wind will let a 32′ stop speak cleanly, while unsteady wind will make the same rank waver.
- Check the room. A dry acoustic will expose flaws in voicing, while a long reverberation will blend stops into a unified chorus.
- Listen to recordings or attend a service. Real music tells you how the stops interact under a player’s hand, which is the test a stop list cannot perform.
If you want to compare how the same family of stops has been treated across different instruments, the pipe organ instruments overview on the Martin Ott site, together with the entries in the organ archive, provides several worked examples of stop lists in context. The pipe length calculator is also a useful way to feel the relationship between a stop’s foot marking and the actual dimensions of the longest pipe.
Choosing a registration for unfamiliar music
When the stop list is new to you, a few practical habits will keep your registration musical rather than mechanical.
- Identify the dynamic level of the piece. Soft movements need flutes and strings; loud movements need principals, mixtures, and reeds.
- Match the period. Baroque music often rewards a clear principal chorus with one or two reeds, while Romantic music tends to ask for strings, foundations, and a deeper pedal.
- Start with fewer stops than you think you need. You can always add another rank, but removing one in performance is harder.
- Listen across the keyboard. A registration that works in the middle of the manual may thin out in the tenor or bottom octave, especially with stopped ranks.
- Trust the building tradition. If the instrument is a French Romantic organ, lean on its strings and reeds. If it is a North German Baroque organ, build choruses with principals and mixtures.
The wider context: stops as part of organ design
An organ’s stop list reflects the choices of a builder about what music the instrument will support, what room it will fill, and what budget it must respect. A list heavy in 8′ principals and mixtures is built for choral and contrapuntal music. A list heavy in 16′ foundations, strings, and harmonic flutes is built for Romantic literature. A list that includes a 32′ stop, a full reed chorus, and a generous Positiv is built for a concert hall or cathedral, and the surrounding case and acoustic are part of the same design.
Reading a stop list is therefore also reading an argument about what music matters. A skilled organist adapts registration to honor that argument rather than fighting it, and a curious listener can hear the choices in every phrase the instrument plays.
Internal links for further reading
Frequently asked questions
What is the difference between a stop and a rank?
A stop is the control at the console, usually a drawknob or tablet, that lets wind into a complete set of pipes. A rank is the set of pipes itself, one per key. The two terms are often used as if they were the same, but technically a stop is the action and a rank is the result.
Why do some organ stops have the same name on different instruments but sound different?
Stop names describe a role, not a fixed tone color. Scale, pipe material, wind pressure, voicing, and the room all shape the final sound. A Flute Harmonique 8′ in a French Romantic organ is a singing, open metal stop; a Flute Harmonique 8′ in a small English tracker organ may use a different scaling and feel much softer.
What does the foot number on a stop mean?
The number is the length of the longest pipe in the rank, measured in feet. An 8′ stop is at unison pitch with the keyboard, a 4′ stop sounds an octave higher, a 16′ stop an octave lower, and so on. It is shorthand for pitch, not a guarantee of voicing.
Are mixtures louder than other stops because they sound more pipes?
Mixtures do sound several ranks at once, but they are not simply louder. They add upper partials to the sound, which our ears read as brilliance. A mixture by itself is rarely effective; its job is to crown a chorus of principals.
What is a coupler, and is it a kind of stop?
A coupler is a console control that links two keyboards so the keys of one play the pipes of the other. It is not a stop, because it does not control pipes of its own, but it is essential for combining stops across manuals and the pedal.
Why are some stops called 2 2/3′ or 1 3/5′?
Those are tierce and seventeenth ranks, sounding a twelfth and a seventeenth above the keyboard. They are usually found inside mixtures and cornets, where they add the characteristic sparkle of Baroque and French chorus work.
Do all organ stops have pipes in the room?
Most do. Some stops use extension pipes, which borrow from the longest pipe of another rank to fill in the bottom of the compass. The builder is honest about this with a small ext. in the list, and the effect is musically identical to a full rank.
How can I learn what a particular stop will sound like before I play it?
Reading the stop list carefully is the first step. Beyond that, recordings, service visits, and conversations with the organist or builder are the best ways. A skilled technician can describe the scale, material, and voicing in terms that map directly to the sound you should expect.
Is a bigger stop list always a better organ?
No. A well-voiced instrument with a focused list of choruses, solo voices, and pedal work is often more useful than a longer list of ranks that are merely present. The best test is how the stops combine under a player’s hand, not the number of drawknobs on the console.
Where can I see real stop lists from finished instruments?
The organ archive collects stop lists from specific instruments, and the pipe organ instruments overview shows how those lists are designed for the music and the room. Studying several lists side by side is the fastest way to train your eye.