How pipe organs make sound

Engineers show how the giant pipe organ at Raleigh’s Holy Name of Jesus Cathedral is built and how it makes sound.

The fingers press the keys, the organ plays, and note by note, the sounds echo off the walls of Holy Name of Jesus Cathedral. “You know, when you fall in love with someone do you have to have a reason,” explains Mayu Allen, an organ tuner with C.B. Fisk and Company in Gloucester, Massachusetts. The company is installing the Cathedral’s pipe organ. “I’ve loved the pipe organ since I first heard it played at a concert when I was in college in Japan. I told the teacher I want to learn everything about it. It’s just, something inside of you just tells you this is it.”

From high above the Cathedral floor, up inside the organ, tonal director David Pike listens to sounds. “The pipes really love speaking from this high up in the room,” says Pike. “They’re getting lots of support from the barrel vault overhead, which helps them project right down the knave very efficiently.”

And down on the Cathedral flood, standing in the center aisle, cathedral music director Michael Accurso agrees the sound is wonderful. “No two organs are alike, so there’s a lot of trial and error involved,” Accurso says. “You have to try out each stop individually as they are all meant for different applications, and so it’s a little bit of a learning process you have to figure out what is good for this situation, what is too much, what is too little.”

But what gives the voice to the massive pipe organ? How does it make those heavenly sounds? To find out, the craftsmen from C.B. Fisk and Company took us inside the massive instrument. We climbed up one ladder and then another, until we were 63 feet above the knave floor, just under the barrel vault of the ceiling. There were pipes all around.

The Holy Name of Jesus Cathedral organ has 3737 pipes. The pipes are made of hammered lead, tin, an alloy of the two metals and even wood. Each pipe plays one note. Small pipes play high notes while large pipes play low notes. The sound each pipe makes depends on what the pipe is made of and its shape.

“The length of the pipe determines the pitch,” explains Pike, as he points to a particular pipe. “This pipe is four feet long and it’s known as four foot ‘C’. The pipe the plays the note ‘C’ an octave up from this is two feet long. And the pipe that plays the note ‘C’ that is an octave lower from this is eight feet long and that’s the pipe right back there.”

There is an even a pipe that plays a note you can’t hear. That pipe is 32 feet long and, as you might expect, plays the lowest pitches of the organ. The pitch of the pipe known as 32 foot “C” is 16 hz. That means it vibrates at 16 vibrations per second, which is below the range of human hearing. This is a note you don’t hear but you will feel.

The pipe organ is a wind instrument. Giant fans fill a wind chest, which sends air through the pipes. To make a sound, a craftsperson cuts a slit into the pipe at the required height. Air blowing through the bottom of the pipe, called the toe, begins to vibrate once it passes over and through the slit.

“The wind enters at the toe and it is formed into a very thin sheet and comes out through this slit,” explains Pike. “The voicers job is to aim the sheet so when it comes out it strikes the upper lip, or the top of the slit, so it comes out in such a fashion that it sets the column in the pipe to vibrating.”

It took eight months in the workshop to create all of the pipes as well as the casing for the organ and then another two months to install the pipe organ in the Cathedral once everything was shipped to Raleigh. It will take about eight more months to tune, or voice the organ, making sure all of the pipes sound perfect when played together.

“The voicing is almost as difficult as the actual construction,” says Allen. She sits at the keyboard playing each note individually, making sure it sounds correct. “First I listen for the volume and then I listen to make sure it doesn’t sound to stringy or too flutey. It needs to be perfect.”

Michael Accurso, the music director who will eventually be playing the organ for services in the Cathedral, says “I think the thing I’m most looking forward to is actually hearing this organ accompany the congregation during the hymns and the liturgy. I think that’s going to be the most moving part to me.”

—Frank Graff 
Frank Graff is a producer/reporter with UNC-TV, focusing on Sci NC, a weekly science series. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!

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