The world's largest musical instrument is in the mountains of Virginia

AYESHA RASCOE, HOST:

In the rolling mountains of northern Virginia. Luray Caverns are celebrating the 50th anniversary of their designation as a national natural landmark. It's also home to the largest musical instrument in the world. Reporter Alan Goffinski takes us there.

UNIDENTIFIED PERSON #1: Good morning.

ALAN GOFFINSKI, BYLINE: All right. Is it cold down here?

UNIDENTIFIED PERSON #2: It's about 54 degrees, high humidity. So it'll be...

GOFFINSKI: On a brisk fall morning, I meet up with the engineers who maintain this renowned musical instrument, the Great Stalacpipe Organ.

Oh, wow, right into it - just walking down the stairs, and then all of a sudden, you're in a cave.

UNIDENTIFIED PERSON #2: Yeah.

GOFFINSKI: To get there, we climb down a narrow staircase and suddenly emerge into the most extensive cave system in the eastern U.S. We wind through dazzling tunnels carved out by water over millions of years, and we make our way through massive crystalline limestone chambers. Around us are towering, dramatic golden rock formations.

Oh, wow. This is wild.

Pools of glassy, smooth water reflect the stalactite formations above. It creates the illusion of an underwater stone city.

My brain doesn't know what to do with this.

This spectacular trek into the depths of the cave brings us to a colossal room known as the cathedral, the heart of the Great Stalacpipe Organ. Someone presses a hidden button, and the cathedral comes alive with bewitching, almost otherworldly melodies that linger, reverberating in the still damp air.

(SOUNDBITE OF GREAT STALACPIPE ORGAN MUSIC)

LARRY MOYER: We're inside the organ right now because all the music comes from stalactites about 3 1/2 acres around us.

GOFFINSKI: Larry Moyer began working at Luray Caverns 42 years ago as a teenager and is now the lead engineer of the Great Stalacpipe Organ. It's a mashup of the words stalactite and pipe organ.

MOYER: I learned from Mr. Sprinkle, the inventor. Leland Sprinkle came through the caverns with his son on his fifth birthday. They would take a little rubber mallet and play a little song on the stalactites, and he got the idea of building an organ.

GOFFINSKI: After years of work and experimentation, in 1957, the organ debuted to the delight of tourists. It has been chiming for tour groups ever since.

(SOUNDBITE OF GREAT STALACPIPE ORGAN MUSIC)

GOFFINSKI: Besides "Shenandoah," it also plays classical tunes.

(SOUNDBITE OF GREAT STALACPIPE ORGAN MUSIC)

MOYER: It's really a percussion instrument.

GOFFINSKI: Each key on the organ, when pressed, sends an electrical impulse to trigger a small hammer which strikes a stalactite, causing it to vibrate and give off a musical note.

MOYER: With the humidity and the environment down here, there's a lot of maintenance to the instrument. There's miles and miles of cabling down here for it. The electronics we build ourselves. There's no Great Stalacpipe Organ store, so we can't go buy parts for it.

GOFFINSKI: For Moyer and his team, it's a labor of love.

(SOUNDBITE OF GREAT STALACPIPE ORGAN MUSIC)

GOFFINSKI: Moyer has devoted decades to the Great Stalacpipe Organ but knows he will have to pass on that responsibility. Two younger apprentices, Stephanie Beahm and Ben Caton, are both soaking up as much knowledge from Moyer as they can.

STEPHANIE BEAHM: It's a lot to learn, but I'm glad we can keep it going.

BEN CATON: I've been here about 18 years. I'm still learning.

BEAHM: It's fun, honestly. You get to say, hey, I work on the Great Stalacpipe Organ. And nobody else can say that. It's still surreal that we get to be a part of it, preserving it for future generations.

CATON: Larry can't retire till we know everything.

BEAHM: Oh, yeah. It's going to be around a long time.

CATON: Yeah.

(SOUNDBITE OF GREAT STALACPIPE ORGAN MUSIC)

GOFFINSKI: On the 50th anniversary of Luray Caverns' designation as a national natural landmark, the engineers responsible for the enchanting sounds that fill the ancient halls remain dedicated to keeping the music alive. For NPR News, I'm Alan Goffinski in Luray, Va. Transcript provided by NPR, Copyright NPR.