Beginners' Guide To The Organ, Non-organists enquire within.... Options

[Teigr]

This thread is for people who don't know anything about organs to find out how they work, what the jargon means and what all the fuss is about.
I hope some of the more experienced organists will chip in with explanations and answers to questions (and corrections, as I'm bound to make some mistakes here!) and anyone is welcome to ask anything about organs (including "could you say that again, but without the jargon?").
The only stupid question is one you don't ask.


So, getting started....

The bit of the organ that you sit at and do things to when you play is usually called the console (sometimes called the keydesk when talking about certain types of organs). The keyboards are called manuals. A typical church organ will have 2 or 3 manuals, and a typical cathedral 4 or 5, but you can find instruments with anything from 1 to 7.
Most organs have a pedalboard. This is a bit like an oversized keyboard, played with the feet.
Most have one or more expression pedals. For the time being, think of them as a variable volume control. They are large tilting pedals set just above the main pedalboard, somewhere near the middle of it. (edit: Usually! On some instruments they are set to the far right.)

Somewhere near the manuals, you'll find the stop controls. Drawstops are knobs that you pull out and are the most usual sort to find on a church instrument. Tab stops are sort of flat switch things that you flip downwards. Either sort will be labelled, most with a number and a name.
The most usual place to find drawstops is on the jambs either side of the manuals. But some organs have them just above the uppermost manual.
Just below the keys, you'll probably find a series of little buttons on the front edge of each manual. These are called thumb pistons.


Imagine a large box, full of pressurized air. Imagine it has 61 holes in it, in a row. Each hole is covered and has a simple pipe (a bit like an upside-down recorder without any finger holes) directly above it, each one slightly smaller than the one before it (so it will give a higher pitched note if air flows through it). The widget (let's call it a pallet) that covers each hole is connected to the corresponding key of a 5-octave keyboard. When you press the key, the pallet moves out of the way and air can flow into the pipe, so that the note sounds.

That's the basic idea of how an organ works.
Each set of 61 matching pipes is called a rank.

Different types of pipes make different sorts of sounds.
So, you'd like to have several different sounds available for each note, which means several sets (ranks) of pipes.

Do you remember the game Stay Alive, with marbles resting on top of two sets of sliders (at 90 degrees to each other)? Each slider had holes in various places, but a marble would fall though only when both sliders were set so that they had a hole underneath the marble?
Organs are like that - to make a pipe sound you need to open two things. A slider (controlled by a drawstop) and the pallet (controlled by a key). If you've got both open, air can move through into the pipe and make a sound.
Until you draw a sounding (or speaking) stop for the manual, you can press the keys as much as you like and you won't get any sound.

Several ranks of pipes, grouped together and intended to be controlled by one manual, are called a division.
Most organs have one division for each manual and one more for the pedals.
This means that each manual has it's own collection of available sounds, and you can play with contrasting sounds by using one hand on one manual and the other on a different one. Or you can change back and forth between different manuals as you play.
You can also change the sounds by selecting different stops (and you can do this while you're playing, but it takes a bit of practice).

On a two-manual organ, the divisions are normally called Great and Swell.

All the pipes of the Swell division are inside a box, with louvred shutters on the front. If you close the shutters, you've basically shut the entire division away inside a closed box. This muffles the sound and makes it seem quieter to the listener. If you open the shutters gradually, you get a crescendo.
You control the position of the shutters using the swell pedal (which is an expression pedal). This is the volume control I mentioned earlier. You're not really changing the volume of sound the pipes produce, but you're changing how much of the sound you allow out of the box.
On a three-manual, the extra one is usually called the Choir and may, like the Swell, be an enclosed division (i.e. be in a box, with a pedal to control the shutters). In this case, the Swell and Choir divisions will be in two /separate/ boxes, and the console will have two expression pedals.

Some organs have more divisions than they have manuals. When this happens, two divisions share a manual and there will be one or more drawstops to control which is active.

If you have 4 divisions, the 4th might be Solo or Positive. If you have 5, you'll get both of those.
I'm sticking with the English names here for the time being. Foreign organs not only have different names, but the character of the divisions may be different, so it's not just a case of translating the names.

Unlike the piano, you can't affect the volume by how hard you strike the keys.
You've got two ways to change volume - open and close the swell box, or add and subtract stops (ranks). The more pipes you use at the same time, the more noise you'll make.
Some ranks are much louder than others, so for a quiet hymn you'll choose different stops than for a loud one, and then you'll add/subtract from there to create a little bit of variety between (or during) verses.

You can also engage things called Couplers which allow you to control the pipes belonging to one manual from a different one. These have names like "Swell to Great" and "Great to Pedal". They are controlled by drawstops, much like sounding stops (ranks) are.

The choice of stops, manuals and couplers that you're going to use for a given piece of music (and you might use several different set-ups within one piece) is called registration.
All the fussing around that you do while playing, aside from actually playing the notes, is known as organ management. (Changing stops, changing pistons, changing the expression pedal(s), changing manuals, etc.)

Explanation of stops (types (flues (flutes & diapasons) and reeds), names, lengths, mutations, etc.) to follow another time, along with explanation of the different types of action and the question of how the box full of air (windchest) works.

Ask if anything isn't clear. Chip in with corrections and clarifications if you've got any (note: I've deliberately simplified a few things).

T.

[Teigr]

I said before that the overtones aren't random.
This is because the string is forced to remain stationary at each end (where it's in contact with the bridge and nut of the guitar). So the default wiggle length is that of the string itself. You can't get one and a half wiggles, because the midpoint of each wiggle is where it moves the most, so you can't have a half-way point like that occurring somewhere the string is held still.
So any waveform occurring on the string needs to be one where the length of the string is divided into a whole number of shorter waves, with no bits left over.

So, the first one you can make is by halving the string, which gives the octave.

Then you can divide it into 3, which gives you an interval of a 12th.

Dividing into 4 (which you've already seen on the guitar), gives the 15th (two octaves).
Dividing into 5 gives you the 17th (two octaves and a 3rd) and into 6 gives you the 19th (two octaves and a 5th).

The further up the series you go, the closer the harmonics get to each other.


In most instruments, the design of the instrument controls which harmonics are most noticeable and which are damped down, which in turn affects the timbre of the sound.


On some instruments you can force a harmonic to sound in place of the fundamental (default) note - you've seen how that works on the guitar already. By resting your finger on the string you force it to vibrate in shorter wavelengths.

On some instruments you do something similar by changing the air-flow. When you change register on the flute (between two notes with identical fingering), you're using harmonics.

The best instrument to hear this in action is the bugle (or cornet or trumpet or similar) - find yourself a friendly cornet player and ask for a demo of how many notes he can play without touching the valves.
I can manage C, G, C, E and (on a good day) G, but I'm rubbish at brass. Your friendly cornet player should get that G and probably the B flat and the C above, possibly more.
Leaving the valves alone means that you're not adjusting the length of the tube (changing that would change the fundamental note). You're doing it all with harmonics.

You might have spotted that the first pair of notes aren't an octave apart. It's very difficult to get the true fundamental on a cornet. I can't do it, and it's not required for normal playing. A brass player friend of mine has managed it, but can't do it on demand.

With Rememberence Sunday coming up, you'll probably hear the Last Post played. It's a bugle call, so the whole thing can be played on a cornet/trumpet without using the valves.



On the organ, if you add a mutation stop, you can reinforce one or more harmonics of your choice, which changes the timbre of the sound.
Stops are labelled with either the length of the pipe or the interval it produces relative to an 8' pipe (which is the default length).

So, let's start with one particular mutation stop as an example.
The pipe length is 2'8", which is written as 2 2/3.
This is equal to one third the length of an 8' pipe, so it gives a sound a 12th higher (octave and a perfect 5th).
Such a stop is often called Nazard or Twelfth.

If you have access to an organ, try this:
Look at the drawstops and find a stop labelled 2 2/3 Nazard (or 2 2/3 Twelfth) and note which division it's on.
Draw that stop and an 8' stop on a different division.
Play a C on the manual that you've drawn the nazard on. Listen to the sound.
Now use the other manual to try to compare it to the C you get from an ordinary 8' pipe.
Then, on that manual, play the G an octave and a half higher, and compare that to the C you're getting from the nazard.
You're not going to want to use a nazard by itself to play hymns!

Now, try drawing an 8' open diapason, a 4' principal, and 2 2/3 twelfth all on the same division. Play a note.
Try taking away the twelfth and seeing what it does to the sound.

That's what mutation stops are for.

If you add too many of them without beefing up the 8' sound, you can overwhelm the basic note.
And, if you experiment a bit with some of the mutation stops, you'll find that they can be rather uncomfortable to listen to.
But when you have a solid combination with plenty of 8' and some 4' stops, you can play around with the very squeaky ones fairly safely. With enough bigger stuff to give a stable foundation, the little stuff is interpreted by your brain as a change to the timbre of the fundamental note, rather than as a separate squeak.

Some stops are called mixtures. Rather than having separate stops for, let's say, the 19th and 22nd, you might find a stop labelled Mixture II 19.22 - meaning a mixture of 2 harmonics, the 19th and 22nd.
Some organs have stops labelled Mixture II, Mixture III, etc. but with no indication of which intervals are in the mixture. (You can work it out, either just by ear, or by sounding the mixture on its own on one manual and comparing it with an 8' stop on another manual.)

So, stops showing numbers that are powers of 2 or which feature fractions refer to the length of the pipe, while ones labelled with 2 or more numbers in the teens and twenties are referring to the intervals above the fundamental.


A combination is a selection of stops, chosen by the organist to give a particular sound.

A church organist will have experimented with various combinations on "his" instrument, chosen some which he considers particularly pleasing and/or useful and programmed the organ to remember them. The thumb pistons mentioned earlier in the thread are used as "shortcut keys" to those combinations. Some organs have toe pistons, which serve the same purpose but are operated by the feet. You press a piston and several drawstops move.
A divisional piston controls stops for a single division. A general piston controls stops across the whole instrument.
Some organs have an electronic system that allows multiple sets of combinations to be stored. You select a particular memory channel (by pressing little buttons) and those LED numbers (see the My Organ thread for a picture) change. A church with several organists may assign each of them a memory channel on which to set up their own piston settings.


More details about particular mutation stops to follow.

T.

[John Robinson]

May I congratulate you, Teigr, on some excellent pieces of writing thus far.

I look forward to the next instalment on mutations. Personally, not having access to an instrument, I should be very interested to learn about the sound of individual mutations (in combination with unison stops, of course), and I hope you can extend the explanation to less common ones such as sevenths, ninths, and possibly even rarer examples such as elevenths and thirteenths. If you could provide sound samples or, at least, point us towards any online samples you know of I should be very grateful.

Indeed this prompts me to suggest that you could perhaps, when this thread is completed, extract all the pertinent information and make a separate web site of it, perhaps including pictures and sound samples.

I have a number of textbooks on the organ which provide a wealth of information, yet none are written for beginners. I feel that what you have written so far could form the basis of an excellent work which would fill this niche.

John