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.
