>> It's the main organ at Duke Chapel.

It's a machine born out of 2,000 years of engineering updates.

>> My favorite organ music is the right organist playing the right piece on the right organ.

>> It's a system of pressure, valves, and vibration.

It's engineering disguised as music.

♪ >> My grandfather was a machinist.

My father was an engineer.

My brother's an engineer.

So just the physical action of it.

>> There are instruments you play and instruments you step inside.

This one comes with a building.

This is what's called a Dutch tracker organ.

Built by Dirk Flentrop.

And even the divisions keep their Dutch names.

>> There's a lot of stuff going on.

What are we looking at, I guess, is the question.

>> There are four keyboards or manuals and a pedal board.

And the organ is distributed all throughout this case.

The top manual is called the echo.

And that's right above us behind doors.

It's rather quiet.

Then we have the bovenwerk.

That's this manual.

And that's way at the very top of the organ.

Then we have the hoofdwerk, which is the main manual with the loudest sounds.

That's right above us above these trumpets here.

Then we have the pedal below us, played with the feet, of course.

And then we have the rugwerk, which is this section of the organ behind us.

♪ >> Four manuals, one pedal board, pipes distributed from floor to ceiling.

Each division positioned to shape how the sound fills the room.

You've all heard the phrase pulling out all the stops.

Well, here this isn't a metaphor.

>> Well, if you see there are all these different stop knobs.

And each one controls a set of pipes.

And they're different sounds.

For example, there's a typical organ sound.

♪ Called a principal or diapason.

And those are the pipes you see in the facade of the organ.

There are also flutes.

♪ And there are also reed pipes.

Here's a trumpet.

♪ Different trumpets at different pitch levels.

♪ >> From here, he'll take us behind him into the rugwerk, the back division.

Part of the around 5,000 pipes in this organ.

>> If you look, you see they're organized from left to right in different ranks or sets of pipes.

Some pipes are open.

Some have caps on them.

Let's take a look at this pipe.

This is a trumpet pipe.

You can see it flares like a trumpet.

And this is the tuning wire.

It changes the vibrating length of the reed tongue.

And that's what changes the pitch.

We're looking at the action for the echo division.

And as you can see, when I push down a key, there's a tracker, a thin slip of wood that attaches to a roller arm.

And the roller arm transfers the action over to here.

>> The ancestor of this machine was called the hydraulus.

It appeared in Hellenistic Greece about the 3rd century BC.

>> And it used water to create pressure to play the pipes.

You'd have one person pumping and one person playing.

♪ >> This machine breathes.

It expands and contracts with the temperature and humidity.

Even a shift in the weather can nudge it out of alignment.

>> Biggest concern for me is if there's a cipher, which is a note that plays when you don't want it.

So we've had very, very cold, dry weather.

And that can affect the organ no matter what kind.

So sometimes you'll have a note that will play.

And you just might hear a little tiny something like that.

♪ >> Duke is cathedral sized.

But most organs live somewhere smaller.

♪ >> We have a great instrument here at Pilgrim.

This is a 1967, I believe, Aeolian Skinner.

About 800 pipes.

Two manuals, two keyboards to play on.

And of course, your pedal board down here.

♪ >> Fewer pipes, smaller case.

Same fundamental system, wind, valves, vibration.

Same need for precision.

>> And so sometimes you want to make sure that nothing has fallen out of tune through the week.

I noticed on Sunday that I think there was a note.

♪ >> That if you can hear is definitely out of tune.

It doesn't sound right.

>> Sounds a bit sharp.

>> That's right.

That's right.

And so it's one of those flute stops there.

And so there are different ways that you can work around that.

You may not use that stop.

You may put it in a different octave so that you can avoid the bad note.

♪ >> Sometimes you adapt.

Shift an octave, change a stop, or crawl inside the chamber and tune the pipe by hand.

>> And the first time that I heard a pipe organ might have been at a wedding or something.

And I remember the way that it filled the space.

And even underneath, through the floor, I could feel the vibration in my feet.

It was really neat.

>> That's the part no blueprint captures, the vibration under your feet, the air pressing against your chest.

It's been around for a long time.

I remember you saying something about it's not just what the organ is playing.

It's also how the parishioners are hearing the music.

What's that all about?

>> Well, they say the best stop on the organ is actually the acoustics of the room.

When Duke Chapel was first built, the Dutch builder Flentrop didn't like what he heard.

>> He did not like the acoustics.

The chapel was built with Guastavino tile.

If you look at the walls, you can see up to about six, seven feet there is a darker stone.

And then above that is this tile that when fired ends up with lots of holes.

And these holes help absorb sound.

Duke found some product to put on the walls to seal the holes.

>> The room stopped absorbing the sound and started carrying it.

>> He came back again and he clapped his hands or however he tested the acoustics.

He liked what he heard and he said he would build an organ for the chapel.

>> Around 5,000 pipes, miles of wooden wire, air under pressure.

It's a 2,000-year-old system still powered by wind.

♪ >> Each organist can make it sound like a completely different instrument depending on how they use the sound.

If they were a chef, it would be spices and ingredients.

If they were a painter, it would be colors on a canvas.

♪