Hello, I’m Ginny Moe, this is Adam Sullivan's Music Theory Blog and you're listening to an episode of The Pipe Organ: its development and design.
Last month's episode was on the basic two types of pipes: how they work and how they sound. You can access again it online anytime. This month's episode is on how the organist controls which pipes actually sound at any given moment.
Pipe organs makes sound when air goes to pipes, so we start with the blower, which sends air to a windchest which is attached to every pipe, with most pipes actually sitting right on top. When one pipe is played it doesn't take much air but when many pipes are played at once it takes a lot of air, reducing the air pressure. So the blower sends air to the windchest through a reservoir, which keeps the air at a constant pressure whether one or 100 pipes are sounding. If you look down on the top of the windchest, you can tell it's not just a big balloon with a lot of pipes sticking out haphazardly. The pipes are arranged in rows and columns, with the toe of any pipe fitting into a hole on the windchest through which wind enters the pipe.
Each column on the chest holds a rank, which is a set of pipes of matching design and sound. Each rank has one pipe for each note, and ranks are usually arranged in order on the chest from the lowest and longest pipes at one end to the shortest and highest at the other end. Two ranks of pipes require two columns and two pipes for each note, three ranks require three columns and three pipes, and so on. The rows on the chest correspond to the notes. Each row holds all the pipes which sound a certain note.
On the sides and ends of the windchest are several kinds of machinery controlling tubes of air inside the chest which allow routing of air to various pipes. These controllers are adjusted through linkages to the console, where the organist sits directing air traffic in the windchest.
Modern consoles normally have one pedalboard and several manual keyboards. The pedalboard has 32 keys, arranged like piano keys but bigger, for your feet, the lowest key being two octaves below middle C, the highest the G above middle C. Each manual keyboard has five octaves, starting at the C two octaves below middle C and going up 61 notes to the C three octaves above middle C. In addition, the console has stops, usually on the sides of the manuals, but sometimes above the top manual. And most organs have pistons, which are little buttons below the keyboard and knobs down by the pedals for the feet to play.
Now how does this console give signals to the windchest?
Stops control a channel of air under a rank of pipes. When a stop is engaged, or pulled, by the organist, air flows into the channel and is available for all the pipes in the rank above the channel. If two stops are pulled, air flows into two channels, three stops pulled and air flows into three channels. If many stops are connected to a keyboard, the channels will be dispersed in columns over several windchests for ease maintenance.
Keys control the rows of the windchest, and every pipe designed to sound the note corresponding to a key is in the the entire row controlled by that key. When a key is pressed, pouches under the pipes in the row open, and if air is in a channel under any pipe, the air is released into a pipe sounding a note.
So, for example, a windchest with eight ranks has eight columns corresponding to eight stops on the console, and on manual windchests, it has sixty-one rows corresponding to the sixty-one keys on the manual keyboard, for a total of 488 pipes. When one stop is pulled, and the organist plays one key, the windchest is signaled to send wind to one rank, and one row. Wind is released to the pipe at the intersection of that column and row, and the one pipe sounds. When two keys are played, two pipes get wind, three keys winds three pipes. If another stop is pulled, another channel of air is available, and one key sounds two pipes, one in each rank, the same note, but different in tone quality. Playing two keys sounds two pipes in each rank, playing three keys sounds three pipes in each rank, for a total of six pipes.
The third main control type on the console, ubiquitous in modern pipe organs, is combination action. Most often it is entirely at the console, for it signals several stops to engage (or disengage) simultaneously. Combinations are activated by pressing the pistons underneath the manuals or near the pedals.
To summarize, in a pipe organ, the blower sends air through a reservoir to the windchest. Pipes sit on the chest arranged in columns of ranks and rows of notes. Organists control which pipes sound by sending signals from a console to the windchest. The majority of these signals are of three types: Keys, controlling rows of notes; Stops, controlling columns of ranks, and Pistons, controlling combinations of stops.
That’s all for this episode, I'm Ginny Moe, and this is Adam Sullivan's Music Theory Blog. Thanks to Adam for hosting this series, The Pipe Organ: its development and design. I hope you’ll check in again next month, when we’ll begin looking at how the sound and design of the pipe organ developed throughout history.
That’s all for this episode. I hope you’ll check in again next month, when we’ll begin looking at how the sound and design of the pipe organ developed throughout history. I'm Ginny Moe, and this is Adam Sullivan's Music Theory Blog (sulliadm.blogspot.com). Thanks to Adam for hosting this series, The Pipe Organ: its development and design.
Showing posts with label design. Show all posts
Showing posts with label design. Show all posts
Monday, February 23, 2015
Saturday, January 17, 2015
The Pipe Organ: Development and Design
Written by: Ginny Moe
The design and music of the pipe organ are a result of its history as builders responded to changing societal needs but more importantly as organists, composers, and organ builders learned to take advantage of developments in science and industrial techniques. This session is on the two main types of pipes and how they speak, or make sound.
At its most basic the pipe organ is a set of pipes similar to flutes or clarinets through which wind blows to make sound usually musical sound and which, in the modern organ, is controlled by an organist who plays a keyboard shaped like a piano keyboard.
Almost all pipes on the modern organ are of two types. Flue pipes comprise the majority of the pipes, and they are almost always made of either metal or wood with a foot through which air flows into the pipe. Most organs also use reeds (sometimes called reed pipes) in which the speaking mechanism is covered by a boot into which air flows, vibrating a tongue. As an example, I currently play a pipe organ which has 17 sets (ranks) of flue pipes and 4 ranks of reeds, plus some extras which combine several ranks of flue stops.
Now the sounding mechanism of these two types pipes is very different. In the flue pipe air enters the foot of the pipe through a toe and is directed toward the mouth of the pipe by a languid. Air goes outside the pipe at the mouth, and the the speedy air outside the pipe reduces air pressure inside the pipe, drawing the airstream into the pipe. This is the Bernoulli effect in practice; the same reason jets can fly. IT IS THE AIR ITSELF WHICH VIBRATES, setting up sound waves.
By contrast, in the reed pipe a shallot extends into the boot. An aperture in the shallot is covered by a tongue. The boot surrounds this mechanism, and air enters the boot through a toe in the bottom. The wind presses the tongue against the shallot, and the tongues bends to cover the the aperture. The tongue springs back, allowing the wind to enter the shallot, and again the Bernoulli effect is observed, and sound is produced by the vibrating tongue. Here, IT IS THE TONGUE, OR REED ITSELF, WHICH VIBRATES.
Since the wind itself makes the sound in flue pipes, the pipe, which shapes the trajectory of the wind, directly affects the sound, and the most noticeable difference is made by the width of the pipe. Very narrow pipes generally produce more overtones, like bowed string instruments, and are called string pipes. Very fat pipes generally produce fewer overtones, like flutes, and are called flute pipes. And the most important pipes in any organ are the medium width flue pipes, called diapasons or principals. Various modifications around the mouth of the pipe also change the sound. The number of strings, diapasons, and flutes varies, but as an example, my current instrument has three independent string ranks, six independent flute ranks, and seven independent diapason ranks.
The reeds make a very distinctive sound, but most of them sound more like each other than they sound like any flue pipe. Usually they are louder, and the variation in sound is mostly caused by different shaped and length tongues and apertures in the shallot. What are often called reed pipes are properly referred to as resonators, and they amplify and change the sound. They are designed in many inventive and sometimes bizarre shapes, some of which make a difference in the sound quality, or timbre.
To summarize, organ pipes are normally either flue or reed pipes. In flue pipes, the air vibrates, and in reeds, the tongue vibrates. Most organ pipes are flues, and the length and shape of the pipe make changes in timbre, or sound quality. The most important pipes are the principals, or diapasons, and if you think of the sound of a pipe organ, you are probably thinking of the sound of the diapasons. They are of medium width, and the narrow pipes are called string pipes, while the fatter pipes are called flute pipes. A few reeds are usually part of a pipe organ, providing distinctive solo stops and fiery color. In them the sounding mechanism is covered by a boot, inside of which a tongue vibrates against a shallot to produce sound, which is then shaped modified by a resonator.
Check in again next month, when the subject will be organ keys, and various ways the keys control the pipework. I am Ginny Moe, and this is a series on The Pipe Organ, and how its design developed throughout history.
Twitter: @GinnyMoeRHSCwebsite: GinnyMoe.net
The design and music of the pipe organ are a result of its history as builders responded to changing societal needs but more importantly as organists, composers, and organ builders learned to take advantage of developments in science and industrial techniques. This session is on the two main types of pipes and how they speak, or make sound.
At its most basic the pipe organ is a set of pipes similar to flutes or clarinets through which wind blows to make sound usually musical sound and which, in the modern organ, is controlled by an organist who plays a keyboard shaped like a piano keyboard.
Almost all pipes on the modern organ are of two types. Flue pipes comprise the majority of the pipes, and they are almost always made of either metal or wood with a foot through which air flows into the pipe. Most organs also use reeds (sometimes called reed pipes) in which the speaking mechanism is covered by a boot into which air flows, vibrating a tongue. As an example, I currently play a pipe organ which has 17 sets (ranks) of flue pipes and 4 ranks of reeds, plus some extras which combine several ranks of flue stops.
Now the sounding mechanism of these two types pipes is very different. In the flue pipe air enters the foot of the pipe through a toe and is directed toward the mouth of the pipe by a languid. Air goes outside the pipe at the mouth, and the the speedy air outside the pipe reduces air pressure inside the pipe, drawing the airstream into the pipe. This is the Bernoulli effect in practice; the same reason jets can fly. IT IS THE AIR ITSELF WHICH VIBRATES, setting up sound waves.
By contrast, in the reed pipe a shallot extends into the boot. An aperture in the shallot is covered by a tongue. The boot surrounds this mechanism, and air enters the boot through a toe in the bottom. The wind presses the tongue against the shallot, and the tongues bends to cover the the aperture. The tongue springs back, allowing the wind to enter the shallot, and again the Bernoulli effect is observed, and sound is produced by the vibrating tongue. Here, IT IS THE TONGUE, OR REED ITSELF, WHICH VIBRATES.
Since the wind itself makes the sound in flue pipes, the pipe, which shapes the trajectory of the wind, directly affects the sound, and the most noticeable difference is made by the width of the pipe. Very narrow pipes generally produce more overtones, like bowed string instruments, and are called string pipes. Very fat pipes generally produce fewer overtones, like flutes, and are called flute pipes. And the most important pipes in any organ are the medium width flue pipes, called diapasons or principals. Various modifications around the mouth of the pipe also change the sound. The number of strings, diapasons, and flutes varies, but as an example, my current instrument has three independent string ranks, six independent flute ranks, and seven independent diapason ranks.
The reeds make a very distinctive sound, but most of them sound more like each other than they sound like any flue pipe. Usually they are louder, and the variation in sound is mostly caused by different shaped and length tongues and apertures in the shallot. What are often called reed pipes are properly referred to as resonators, and they amplify and change the sound. They are designed in many inventive and sometimes bizarre shapes, some of which make a difference in the sound quality, or timbre.
To summarize, organ pipes are normally either flue or reed pipes. In flue pipes, the air vibrates, and in reeds, the tongue vibrates. Most organ pipes are flues, and the length and shape of the pipe make changes in timbre, or sound quality. The most important pipes are the principals, or diapasons, and if you think of the sound of a pipe organ, you are probably thinking of the sound of the diapasons. They are of medium width, and the narrow pipes are called string pipes, while the fatter pipes are called flute pipes. A few reeds are usually part of a pipe organ, providing distinctive solo stops and fiery color. In them the sounding mechanism is covered by a boot, inside of which a tongue vibrates against a shallot to produce sound, which is then shaped modified by a resonator.
Check in again next month, when the subject will be organ keys, and various ways the keys control the pipework. I am Ginny Moe, and this is a series on The Pipe Organ, and how its design developed throughout history.
Twitter: @GinnyMoeRHSCwebsite: GinnyMoe.net
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