Resonance, Caves, and Music

Exploring the Luray Caverns in Virginia when we came across this gem:

A 'stalacpipe' organ.

A Mr. Sprinkle spent 3 years in the 1950s picking out stalactites that had the requisite resonance frequency (Well, apparently he had to shave some of them down to get the pitch just right). He then attached a solenoid to strike them when signaled by the key on the 'organ' and a microphone to pick up the resulting sound to amplify on a speaker.

Now, when we hit the unit on standing waves and resonance in physics, I'll have another example to give my students!