The Great Stalacpipe Organ is an electrically actuated lithophone located in Luray Caverns, Virginia, USA. It is operated by a custom console that produces the tapping of ancient stalactites of varying sizes with solenoid-actuated rubber mallets in order to produce tones. The instrument’s name was derived from the resemblance of the selected thirty-seven naturally formed stalactites to the pipework of a traditional pipe organ along with its custom organ-style keyboard console. It was designed and implemented in 1956 over three years by Leland W. Sprinkle inside the Luray Caverns near Shenandoah National Park in Virginia, USA.
This is an atrocious video from Ripley’s Believe it or Not, but it does have some shots of the organ in operation: