by Trevor Cox
Besides flutes, there is evidence of 30,000-year-old percussion and scraping instruments, along with the prehistoric use of ringing rocks and cave acoustics. A xylophone made from stone might seem an implausible musical instrument, more likely to produce a disappointing clunk than a resonating bong, but certain stones can generate notes. Examples are found around the world: from the tall slender rows of musical pillars in the Vittala Temple in Hampi, India, which ring like bells, to the large rock gongs in the Serengeti, Africa, made from boulders and covered in percussive marks, which make metallic clangs.
Nicole Boivin, from the University of Oxford, has studied the rocky outcrops at Kupgal Hill, southern India. These formations contain boulders of dolerite that create loud ringing tones when hit with granite stones. But did ancient people ever play the rocks? The best evidence is the Neolithic rock art alongside the percussion marks, showing that the site was used for many thousands of years.19 In a cave at Fieux à Miers in the south of France, there is a large, 2-meter-high (about 7-foot) stalagmite that rings like a gong. Fractures from when it was struck have been dated to 20,000 years ago.20 Dating percussion marks on rock gongs can be difficult, but in this case the new layers of calcite over the damage give an inkling of the age. What’s more, this cave was only recently unsealed, and other prehistoric artifacts found inside indicate when it was occupied.
When I was younger I used to go caving, and I was strictly warned to be very careful of delicate stalactites and stalagmites. Earlier, in the mid-twentieth century, attitudes were more relaxed, allowing an act of “vandalism” to produce the most fantastical stone instrument. Luray Caverns in Virginia contains the Great Stalacpipe Organ, which entertains visitors and occasionally accompanies brides marching down the subterranean isle.
Andrew Campbell, the tinsmith from the town of Luray, discovered the cave back in the late nineteenth century. A report by the Smithsonian Institution in 1880 commented, “There is probably no other cave in the world more completely and profusely decorated with stalactite and stalagmite ornamentation.”21 When I visited, a year after my trip to Wayland’s Smithy, I was amazed by the number of formations. They seemed to cover every surface. The curators have lit the cave with bright lights, giving visitors the impression that they’re walking around a film set.
The organ is toward the end of the tour. In the middle of the cathedral cavern, among a forest of cave formations, sits an item that superficially resembles a regular church organ. But when a key is pressed, instead of compressed air blowing through an organ pipe, a small rubber plunger taps a stalactite, which rings and makes a note. The current instrument uses stalactites covering 1.4 hectares (3.5 acres) of the cavern. “It is the largest natural musical instrument in the world,” the tour guide proudly announced in a staccato Virginia twang so rapid that every other sentence was unintelligible.
With each key connected to a different cave formation, the organ can play thirty-seven different notes. A magazine article from 1957 reports, “Visitors stand enthralled as melody and chords play all round them. No twinkly tunes these, but full-throated music rolling through the cavern.”22 Apparently I heard a rendition of “A Mighty Fortress Is Our God,” a sixteenth-century hymn by Martin Luther, but I struggled to pick out any semblance of a tune. It was my own fault; I stood very close to the stalactite that plays the musical note B-flat to get a good view of how it worked. But this meant that the volume balance between the different notes was awry. The cave formations playing the notes are strung out over such a large area that many were too distant and quiet. From where I stood, the music appeared to have only five notes, and it was more like a piece of avant-garde experimental music than a hymn.
In the middle of the cavern the balance between notes is better, and the reverberance of the cave adds an ethereal quality to the music. A combination of the natural ring of the stalactites and reverberance in the cavern means that notes start and end vaguely. By standing close to one stalactite, I could examine the quality of one note in detail. It reminded me of a metallic gong or church bell.
The Great Stalacpipe Organ was the brainchild of Leland W. Sprinkle, an electronic engineer whose day job was at the Pentagon. While visiting the cavern, Sprinkle heard a tour guide hit a cave formation with a rubber hammer, and he was inspired to make the instrument.23 He then spent three years armed with a small hammer and a tuning fork, searching for good cave formations. When he tapped a stalactite, it would ring with the cave formation’s natural resonant frequency. So his task was to find stalactites that produced a beautiful ringing tone and also had a natural resonant frequency close to a note in a musical scale. As Sprinkle discovered, the most visually impressive formations often failed to produce a sound that lived up to their appearance. Only two formations were naturally in tune, so others had to be altered. Sprinkle used an angle grinder to shorten these stalactites, thereby raising the natural frequencies of the cave formations, and eventually he produced a scale of notes that were in tune.
Sprinkle certainly did not spend a long time worrying about appearance. The Stalacpipe Organ looks as if a cowboy electrician botched the cave’s wiring. The mechanisms are crudely bolted onto neighboring cave formations and walls, and wires hang loosely and without organization around the space.
Leland Sprinkle is not the only person to become obsessed with making the perfect rock instrument. In the nineteenth century, Joseph Richardson took thirteen years to construct a large stone xylophone out of hornfels slate from the English Lake District. According to the Journal of Civilization, Richardson was “a plain unassuming man, with no refinements of education, but possessed of musical talent.”24 The vast instrument currently resides in the Keswick Museum and Art Gallery in Cumbria, where visitors are actively encouraged to play it.
The stones of this “rock harmonicon” span two rows over 4 meters (13 feet) long, with steel bars and bells on two upper levels (Figure 2.2). The bass notes are poorly tuned, and the tone varies across the instrument. Some stones ring beautifully, like a wooden xylophone, while others sound like a beer bottle being struck with a stick. A better percussionist might be able to coax a more musical sound than I did. One historical account recalls, “The tones produced are equal in quality, and sometimes superior in mellowness and fulness, to those of a fine piano-forte, under the hand of a skilful player.”25 One of the key skills of a good percussionist is the ability to make the mallets rebound quickly, so that they do not inhibit the vibration of the instrument. According to the museum’s curator, the whole instrument plays sharp; that is, the frequencies of the notes run higher than the standard scale. To tune the instrument, Joseph Richardson chipped away at each slate bar, gradually raising the frequency of the note. If he removed too much stone, the slate played sharp and there was nothing that he could easily do to flatten the note.
Figure 2.2 Richardson’s rock harmonicon.
According to the Journal of Civilization, the Richardson rock harmonicon was so large that it needed three of Joseph Richardson’s sons to play it, “one playing the melody, the next executing a clever working inner part, and the third the fundamental bass. Its power extends to a compass of five octaves and a half . . . extending, in fact, as high as the warble of the lark, down to the deep bass of a funeral bell.”26
I managed a plodding rendition of “God Save the Queen”—quite appropriate, since Queen Victoria had requested command performances at Buckingham Palace by what a handbill advertising a public concert described as the “Original Monstre Rock Band.”27 According to the Times, the first performance was “one of the most extraordinary and novel performances of the Metropolis.”28 The Richardson family toured Britain and the continent playing music by Handel, Mozart, Donizetti, and Rossini.29
John Ruskin, the great Victorian writer and critic, used to own a lithophone made from just eight rocks, and in 2010 a new instrument was constructed for Ruskin’s old home in the English Lake District. Star percussionist Evelyn Glennie gave a celebratory performance on the new l
ithophone, which has forty-eight keys arranged in a sweeping arc around the player. The instrument contains green slate, blue granite, hornfels, and limestone from various local valleys and mountains. Writing in the Guardian newspaper, Martin Wainwright described the different sounds: “The clinker gives a short, martial note; the green slate a pure, clear, soft sound.”30
The team of geographers and musicians that constructed this new instrument also investigated what makes a rock ring. The size, shape, and material determine the frequency of the sound. But what intrigues me most is why some stones go bong while others merely clunk. When a percussionist strikes a stone that rings, the energy is held in the rock for some seconds, with the stone’s vibration being gradually transformed into sound waves in the air that you hear. The rocks that go clunk lose their energy too rapidly within the stone. Good wineglasses ring when gently tapped. But rest a finger on the edge of the glass, and the sound disappears almost immediately. The friction between the glass and the finger dampens the vibrations and prevents the ringing. For rocks, the damping comes from the internal structure of the stone rather than your finger.
In 2010, I interviewed violin manufacturer George Stoppani for a BBC radio program about how to choose the right wood for the best-sounding violin. He went around his dusty workshop tapping pieces of wood to allow me to hear the different sound qualities. Only wood with the right grain density and microscopic structure produces a clear tone, which rings on for a few seconds—evidence that it can be used to make a world-class violin. It is similar with rock.31 Within the stone, vibrations are being passed from molecule to molecule. If there are any cracks or hairline fractures, then it is more difficult for the vibration to travel within the rock and the stone will ring less well. In the age of steam, wheel tappers working on the railways exploited the same principle, checking mechanical defects invisible to the naked eye by tapping the wheels of the trains with a small hammer. Lack of a satisfying ring indicated cracks, which could lead to a catastrophic failure of the wheel. But there is more to this than just cracks. Hit a piece of sandstone and it will not ring, whereas a piece of slate, like those I played at the Keswick museum, can impersonate a gong. Both stones originated from layers of sediments, but slate has been transformed by hundreds of millions of years of pressure into a denser material with a more ordered molecular structure. Vibrations can pass more easily between the neatly arranged molecules in slate than between the loosely packed grains of sand in sandstone.
My wife likes to have long phone calls while wandering around the house. As she walks between rooms, her voice changes in fascinating ways, both for her family in the house and for people at the other end of the phone line. Her voice is stronger and harsher in the kitchen because of the hard, reflective tiles and flooring, and clearer and warmer in the living room with soft furnishings, which deaden the sound. The microphone in the handset is picking up a mixture of the sound that travels straight from her mouth and the reflections bouncing off the walls, floor, ceiling, and objects in the room. She cannot sneak into the bathroom during a phone call with me because the bright reverberation is a dead giveaway. Size also matters: larger rooms tend to create a livelier, booming sound.
Now imagine you are prehistoric person wandering around a dimly lit cave system. Your voice will alter as you move from cavern to cavern, through narrow entrances and down tortuous tunnels. The sound quality varies because of the changing patterns of reflections from the rocks. In large caverns a booming reverberance might be heard, in extreme cases mimicking the sound of a church. But in smaller caverns and tight squeezes, the key acoustic effect is coloration.
An old staff room at my university had an amazing ability to color sound. It was a plain, narrow, rectangular room with chairs lined up on either side; it was like a waiting room at a train station. The first few times I went into the room I noticed a strange distortion as other people spoke. Moving my head back and forth dramatically changed the timbre of my colleagues’ voices. With my head in one position, their speech sounded very bassy and powerful, but elsewhere their voices went all tinny, distorted, and horrible. Colleagues probably wondered if I had been drinking, as I gently swayed back and forth listening to our lunchtime conversations, scientific curiosity trumping self-consciousness.
As I moved my head from side to side, voices in the room changed as if someone was rapidly altering the settings on a hi-fi’s graphic equalizer. This coloration was caused by a change in the balance of the sound, with some frequencies being boosted while others were suppressed. It might seem odd to talk about the color of a sound, but many of the words we use to describe sounds are appropriated from elsewhere: bright, warm, dead, live. The link between color and sound goes back many centuries, with Sir Isaac Newton spotting the similarity between the distance his prism spread out light colors and the lengths of strings needed to sound out a musical scale.32
Even today, acoustic engineers carry out measurements using “white” and “pink” noise. When paints are mixed together they form a particular color because the various pigments alter the frequency balance of the reflected light. Blue paint reflects light of a higher frequency than red paint. Similarly, acoustic engineers use colors to describe the dominant frequencies in sounds. White noise contains all frequencies in equal quantities and hisses rather like a poorly tuned radio. Pink noise contains more low frequencies, so it rumbles with a more thunderous quality.
Stairwells with two large, flat, parallel walls are a great place to hear coloration. Just clap your hands and you should hear a shrill, high-pitched note. This is a flutter echo, which is caused by sound bouncing back and forth between the walls, passing your ears over and over again at regular intervals. The frequency of the tone depends on how long it takes for the sound to go from your ear to the walls and back again.33 If the stairwell is narrow, this round-trip is quick, the reflections from the wall arrive quickly, one after another, and a high-pitched note is heard. For wider stairwells, there is a longer delay between the reflections you hear, and a lower frequency results.
The most extreme flutter echo I have experienced was in Spiegelei, a temporary work of art at Tatton Park, Cheshire, England, by artist Jem Finer. This was a spherical camera obscura, a metal sphere about 1 meter (3 feet) in diameter on top of what looked like a large garden shed. Stick your head into the middle of the sphere and you could see images of the park projected upside down onto the inside—the visual distortions being inspired by the artist’s memories of taking drugs in the park as a teenager. The exhibition catalogue described the sound inside as “distorted and deranged”—fitting for a work that was playing on the absurdities of gravity.34 It was fascinating to see how many people experimented with the acoustic once they poked their head inside the sphere. Like a stairwell, the sphere provided sound reflections arriving at regimented intervals. As the curved walls of the sphere focused the sound, the reflections were particularly strong and the coloration especially marked.
You are unlikely to find a perfect sphere in a natural cave. Nevertheless, distinct coloration is heard in caverns. Would prehistoric man have exploited the coloration caused by tight squeezes in caves or the longer-lasting reverberation offered by large caverns? It would be extraordinary if our ancestors had overlooked these effects, especially when you consider how poor the lighting was and how unusual such acoustic effects would have been in an era before buildings. Indeed, starting in the 1980s acoustic archaeologists have been building up evidence that rock art is found in places where the sound is especially noteworthy. One of the pioneers of this work is Iegor Reznikoff:
A remarkable discovery in the study of ornate caves is the relationship between painted red dots in narrow galleries, where one has to crawl, and the maxima of resonance of these galleries. While progressing in the dark gallery, crawling and making vocal sounds, suddenly the whole gallery resonates: you put the light of your torch on, and a red dot is there on the wall of the gallery.35
Sound also appears to have influenced wha
t our ancestors painted. Acoustic archaeologist Steven Waller tried to put the work on a more robust scientific footing by statistically analyzing what appears in each acoustic zone. In a paper in Nature he wrote, “In the deep caves of Font-de-Gaume and Lascaux, the images of horses, bulls, bison and deer are found in regions with high levels of sound reflection, whereas feline art is found in regions of the caves with poor acoustics.”36 It seems that our ancient ancestors were exploiting cave acoustics as they told stories around their drawings, with tales of loud hoofed animals being amplified by reflections, whereas quiet cats called for no sonic reinforcement.
The sheer volume of evidence that prehistoric rock art was influenced by cave acoustics is quite persuasive. But David Lubman, a retired aerospace engineer who has been applying acoustic science to archaeological sites, warns that correlation does not necessarily mean causation.
I met David in a Vietnamese restaurant in Los Angeles to discuss his work in archaeoacoustics. His wife, Brenda, accompanied us and took the wise precaution of bringing her own car to allow an early escape, because once you get David talking about his favorite subject, it is very difficult to stop him.
“High praise for Dauvois [another researcher] and Reznikoff, and their discovery of that correlation,” said David. “I think [this] was a turning point for me.”37 He went on to explain that a proper scientific sound source would have been better than using Reznikoff’s voice to test the caves, and that the whole methodology is vulnerable to experimenter bias. David’s hypothesis is that the painters chose nonporous rocks for their art because they would be easiest to paint. By chance, nonporous rocks also provide the strongest reflections. Sound waves cannot penetrate an impervious surface; the sounds just bounce off it. In contrast, porous rock has microscopic holes, air channels that the sound waves can enter. In acoustics, air is modeled as a viscous fluid, like molasses, except much runnier. And like molasses, air does not like being forced into the small channels. As sound enters these tiny holes in the porous rock, the vibrating air molecules carrying the sound wave lose energy to heat. Consequently, porous stone provides weaker reflections than do nonporous rocks.