Organ Registration Basics
Pipe and Electronic Organs
One of the most unique aspects of the organ is its ability to produce a wide variety of tone colors. Most organs contain or simulate these basic types of pipes:
- Flues - (Pipes that produce sound by means of air passing through an opening in the side of the pipe wall.)
- Reeds - (pipes that produce sound by passing air over a thin metal strip called the reed
There are also different types of flue pipes. The thin string pipes produce more harmonics or overtones than there fatter cousins the diapasons. The diapasons or principals produce a uniquely full and rich sound. The ratio of pipe height to pipe diameter determines it's scale. the flute pipes have a large diameter. This causes their tone to be full but have less harmonic content then the other flue pipe
The reed pipes are made of a thin metal strip that vibrates when air is forced over it. This excites a column of air in a pipe called the resonator. These pipes are given names such as trumpet, tuba, oboe, and clarinet.
Organ voice stops are typically given a sound name and a octave indicator. The name will tell you what kind of sound the pipes will produce. The octave indicator is usually given in feet. The longer pipes have lower bass pitches and the shorter pipes have higher treble pitches. The main pitch length for keyboard pipes is 8' while the main pitch for the pedals is 16'. Only the lowest pipes will be the approximate length of the stop name; the pipes will reduce by one half for each octave so many pipes will be quite small. Although electronic organs do not have pipes the naming convention still is used.
Each organ is unique and even if it is a standard model it will be in a unique acoustic environment(the space in which it sounds). It will be necessary listen to each stop individually and also in comparison to the other stops. It will take some time to get a real understanding of each organ's sounds. Focus on what stops can solo and which stops can accompany them.
Thinking in terms of sound sections is one way to approach registration. The diapasons are the basic organ pipes usually full and rich in character. The flutes are light and clear while the strings are usually softer and warmer in tone. The reed stops are harder to group but most organs will have bright and loud trumpets, thin and piercing oboes and maybe a round and full horn stop.
Mutation stops add partial harmonics to other stops so are normally not used alone. These can be identified by their fractional pipe length names 2 2/3, 1 1/3, 2 2/5 and so on. Mixtures also add brightness but do so by sounding several pipes together. These are also used primarily in combination with other pipe ranks to produce a full bright sound.
Encyclopedia of Organ Stops - This is an excellent resource for understanding pipe organ stops and their names.
Registration on drawbar organs such as Hammond or Gulbransen requires a different approach. These instruments produce sound by combining the partials of a harmonic series to create the organ's timbre. Each individual drawbar produces a nearly pure tone that is mathematically related to the others. The tone is not totally pure on purpose as this makes the over-all effect more rich and organ-like. Pulling out the drawbar causes a gradual increase in volume for the selected partial. See the chart below to see a typical drawbar lay-out.
16 - The octave below basic pitch - basic/2
5 1/3 - 2nd overtone for 16 pitch - 16 pitch*3
8 - The basic pitch -basic * 1
4 - The octave above basic pitch -basic*2
2 2/3 - the 2nd overtone -basic*3
2- the 3rd overtone - basic*4
1 3/5- the 4th overtone - basic*5
1 1/3 -the 5th overtone - basic*6
1 1/7 - the 6th overtone - basic*7
1- the 7th - basic*8
Using the 8 bar by itself gives a flute - like sound. Add more overtones to increase the brightness of the sound. Make the higher overtones louder than the basic pitch the get thin string-like sounds. Use only odd multiples of the basic to get hollow clarinet type effects. The 16 bar and its overtone partner, the 5 1/3 bar, are good for playing solo lines. The effect is vaguely like men and women singing a melody each in their own octave.
The drawbar organs often use rotary speakers (Leslies) to produce a modulated tremolo type sound effect. Use this to add warmth and motion to the sound but be careful since it can also reduce the sound' s clarity.