The pipe organ is not well presented in the major American orchestration/instrumentation texts causing most non-organist composers to be naive about the instrument. This essay is intended as a supplement to aid composers with understading and communicating in the language of organists.
The concert or church organ is a wind instrument made up of hundreds to thousands of pipes. The few pipes you see in the front of the case (called 'prestant') usually DO speak but represent only one stop on the instrument. Click -here- to see a pipe chamber from the organ at Old First Presbyterian.
The pedal ranges from written low C under the bass stave to the E above the stave. But unlike the piano, the organ is a transposing instrument. Even the pedal can be assigned to play in the highest treble range by pulling out the 2' or even 1' stops. This gives the organ the widest range of pitch possible. From beyond the very bottom to the top of human hearing.
Its dynamic range is from the quietest pianissimo to the loudest thundering and blasting fortissimo. The organ easily holds its own with brass or full orchestra.
A typical organ has one foot pedal board and two or three keyboard manuals - but some have as many as five manuals. And as you'll soon discover every organ is a totally unique beast with its own overall timbral characteristics and construction. This varies greatly from builder to builder, from country to country, and in which century the organ was built. Some examples: English organs have a different sound from French and German organs. Organs built in the time of Bach were made to best project contrapuntal music clearly. Romantic French organs from the 19th century were made with a lot of 8' foundation stops to create a rich sound for the more chordal based/homophonic music of that time. And unlike ancient orchestral instruments, older organs are still regularly used in their original settings and can last for hundreds of years. They are sometimes not tuned in modern equal temperament - major 3rds and tonalities remote from C major will sound striking and strange at first. The practical meaning of all this for us as composers is that unless you are writing for a specific instrument, you can't be completely sure of what you are going to get sonically. There is a collaborative effort between the composer and the performer. The performer will 'register' your piece. He/she gets a hand at orchestrating what you've written.
That said, there are certain staples of timbre available on most good sized organs.
A stop is usually a knob pulled out to activate a set (or multiple sets) of pipes called a 'rank ' which usually covers the full range of the keyboard or pedal board. A small practice organ at the conservatory might have three stops -one per manual plus the pedal- whereas the huge organ at Yale's Woolsey Hall has 166 stops and 12,573 pipes. More typically you will find between 10 to 40 stops.
The organ has two basic types of pipes: Flue and Reed
Flue stops are created from either metal or wooden pipes. Air is forced into the 'toe' at the bottom and comes out a hole cut a few inches above much like a tin whistle or dog whistle. There are several varieties of these stops. Differences in timbre are created by the width of the pipe and how large the speaking hole is. Narrow pipes create a string like sound with a lot of higher partials. Wide pipes create flute like timbres. In fact the organ is capable of a very realistic flute sound with chiff. A tremulant can be turned on to add vibrato and expression to the sound. Heavy tremolo and high wind pressure give theater organs -"behold the Mighty Wurlitzer"- their characteristic sound.
The staple sound of all organs is called the "diapason" (dy-ah-pa-zen). A variant is called the 'stopped diapason' where a stopper is placed in the top of the pipe to close it off and create a pitch one octave lower than the actual length of the pipe. In this way you can get a deep 16' sound out of an 8' long pipe. The stopped diapason sounds like a somewhat muted diapason. You will usually find both on an organ.
Reed stops are created by pipes that have metal tongues that beat against a hard surface (think of a saxophone reed and mouthpiece). These reeds in fact often are designed after clarinets, cromornes, trombones, and trumpets. They have a lot of individual character. The intensity varies from country to country. French reeds tend to be more raspy and blatant than German or English reeds. The timbre is affected by how the builder and tuner 'voice' the reed which means how it sits, how much curve the tongue has and how thick it is. - Click here - to hear George Becker play an ancient Spanish piece on just the reeds.
Two special stops are the Mixture and the Cornet both of which consist of several ranks of pipes.
Most larger German and American organs have mixture stops in each division. A mixture adds incredible brilliance and thickness to the organ plenum (full organ). A mixture is made up of several pipes sounding for each key pressed- usually between 4 to 6 per key. These flue pipes are short and add very high partials to the timbre. The mixture is used in conjunction with other basic stops and helps the organ sound cut through. - audio example-
Cornet: the cornet (cor-nay) adds three higher partials to the basic sound. Specifically a 2nd inversion major triad one octave above the key you press. -audio example-
Length of pipes
16' (16 foot), 8', 4', 2' etc. What does this mean? A middle C played at 8' pitch on the organ will produce the C that corresponds to the same exact C on the piano - one line underneath the treble stave. The deepest pipe of an 8' set is literally 8 feet long. So an 8' stop is at NON-transposed concert pitch. The organ gets its richness however by combining many stops at once. The 4' Octave stop for example adds a whole level of brightness and would be the same as playing middle C on the piano and the octave above simultaneously. In this way, you can keep going adding stops and tack on a 2' and even a 1'. That would create a very bright and loud basic organ sound. Every key you play would in effect be the same as playing quadruple octaves on the piano. That full rich basic sound is called the 'plenum'.
On the other end of the scale are the deep stops especially used in the pedal. As stated above, the pedal goes down to low C -the 'cello C- and so do the manuals but if you pull out a 16' stop you can go one octave lower- which is lower than a double bass' low E string. A 32' stop allows even one more octave down which is mostly felt as in-tune room shaking rumble and not heard as a pitch. The organ at Yale even has a very rare 64' Gravissima stop. Typically these are added to create a deep bass feeling while keeping an 8' stop on top. Also you have not only a choice of combining all different octaves for a huge, bright, or unique sound (16' and 1' only for example), you can also combine different timbres of varying stop lengths, e.g. 8' cromorne, 8' trumpet, 4' clarion and 16' clarinet together would create a blasting ancient reed effect. Whereas an 8' stopped diapason and a vox celeste would create a chorus effect because the entire vox celeste is tuned slightly sharp.
The 16' reeds can produce a very heavy and incisive bass but can also be assigned to a single manual and used as a solo. You could for instance have a 16' clarinet or 8' cromorne on the top manual -swell or choir- while playing a string or flute accopaniment on the great manual.
All of the pipes are set into different boxes -divisions -which correspond directly to the pedal, great -lower manual-, swell, and choir which is the top manual. The swell and choir usually have shutters that can be opened and closed -quickly if desired- using a foot pedal. This can be used to create crescendos and decrescendos. The pedal and great do not have use of these expressive shutters and remain open.
Organs may also have an expressive device called a tremulant which adds vibrato to the sound overall sound or the sound on just one manual. The tremulant speed of vibration is fixed at a constant rate. - Click to hear the tremulant-
You can link the different manuals and pedal (divisions) together so that you can play some of them or all of them simultaneously from hitting just one key or pedal. The tabs that link them are called couplers. This allows for a great mass of sound. You can simply link the swell to the great at 8' pitch which would then give you all the stops that you've pulled out on the great plus all of those you've pulled on the swell. Or you can couple the manuals and pedals together by different feet- causing transposition by octaves. For example you can couple the swell to the great at 4' which would give you all the stops you've pulled on the great plus all the swell stops but the swell stops would sound an octave higher than the great. Likewise you can couple at 16' or 2'.
Here are some things to keep in mind:
The organ sustains a note at exactly the same volume as long as the key is held down. There is no dying away as on a piano except for closing the swell shutters. Just as in percussion writing, you should be very certain to notate exactly when you want the player to let off the key. If you are composing music on the piano but writing for organ, remember that what you may be able to sustain with the piano pedal will be completly naked and exposed on the organ.
The left hand should take the higher bass and lower tenor parts, the pedal is quite agile at playing single bass lines legato as well as hitting two note chords.
The pedal can play a cantus firmus at a high pitch level. You could assign a 2' stop to it and it would carry higher than the manuals.
There is no sustain pedal - organists will strive to create a legato effect by holding down keys and substituting one finger for the other to help get around on the keyboard.
You can change stops mid-phrase because the organist either has access to electronically programmed piston settings or will call on an assistant to pull stops.
Stereo echo effects - the divisions sit up in large boxes high above the organ consel to its left and right. A part could be played on one manual and then echoed on another. Sweelink enjoyed this in his Echo Fantasias.
Tempo markings should be only approximations, the final decision left up to the performer because every organ is housed in a hall with different amounts of reverberation. In a large hall a very rapid passage on a loud set of stops would come out sounding muddy. A very small hall or living room organ can make the instrument very exposed/naked but you would also hear everything clearly.
There are thousands of pieces for pipe organ but if you are looking for some more or less modern and available recorded pieces here is a brief list:
Ligeti: Volumina, Etudes for Organ (Harmonies and Coulée)
Olivier Messiaen: Numerous organ pieces. Should be easy to find at a major record store.
Hindemith: 3 Sonatas
Keith Jarrett: Hemispheres - an improvisation. Purely mechanical organs can produce amazing sounds by having their stops pulled out only partially.
Ives: Variations on America
Gothic Records - carries a variety of organ recordings.