The fact that some rocks ring quite nicely when you hit them is not up there on the list of distinguishing tests that we teach petrology students. Most of us probably think of it as no more than a neat curiosity. But as a way of interesting the public, and especially potential future Earth scientists, in rocks, their musical attributes have great potential.
The world’s first rock instruments
Cumbria has a special place in the story of musical rocks (which is nicely encapsulated by Mike Adcock on his website:
www.lithophones.com). Several local families discovered that hornfelses close to the Skiddaw granite often ring beautifully, and after years of patient collecting to get all the requisite notes, constructed large lithophones (effectively stone xylophones) that were a minor Victorian sensation. One such family, the ‘Till Family Rock Band’ even went on tour in North America. The Till family were also responsible for building Ruskin’s own instrument, which he kept in his house at Brantwood.
‘Ruskin believed in local materials to do local things’, says the University of Leeds’ Bobbie Millar, who co-ordinates the project. ‘He wanted to engage people with the landscape. Ruskin’s instrument was taken to the Ruskin museum, where it was damaged, so we thought it would be fun to make a 21st century rock instrument for Ruskin’s house’.
One working instrument is on display in the Keswick Museum, and my first introduction to ringing rocks was an excursion with Cumbria geologist Alan Smith and Murray Mitchell to investigate the site where Alan had deduced the old instruments were sourced from. The trip was very productive; the rocks rang to plan, and it was also possible to see how metamorphic petrology had conspired with weathering to produce slabs suitable for instrument making, by picking up on subtle differences between cm-scale beds and exaggerating them by producing different proportions of cordierite (weathered) and andalusite (resistant).
The aim of the Ruskin Rocks project was altogether more 21st century. We would build a musical instrument, but rather than go out and seek the right stones, our colleague Kia Ng, Director of the Interdisciplinary Centre for Scientific Research in Music at Leeds, would use music technology to decide on the dimensions for ringing slabs, and they would be cut and tuned accordingly.
Educational
To make a viable project with such a bizarre objective we had to find ways to make it useful. The bulk of the funding was obtained from Natural England through Defra's Aggregates Levy Sustainability Fund, which meant that we had to find ringing rocks in aggregates quarries (yes, they sound different as they go through the crusher, but it’s a bit late by then!). A key part of the project was to make links between local communities and the quarries, and to provide educational resources. To do this, Bobbie involved local geologists Eric Johnson and Alan Smith.
‘This is all about engaging children’, says Bobbie. ‘What we want to do is get the children to play the rocks and understand more about the landscape. We’ve involved six primary and three secondary schools, who have gone out to a quarry and collected their own musical rocks’.
At the same time, the children find out about geology; particularly what goes on in quarries and how they contribute to the region. The support of aggregate and quarrying companies throughout Cumbria was outstanding, despite the economic climate, and the project could not have happened without them. We hope that it has earned them plenty of good PR along the way.
As well as making the instrument, we needed somewhere to keep it that people could go to play it, and here the support of the Ruskin Foundation at Brantwood was key. Director Howard Hull was an early proponent of the project and offered the use of a separate building, the Linton Room, next to the main house at Brantwood for a permanent display. This meant that we could prepare geological educational materials to go alongside the instrument, and explain something about the different rocks that were in the instrument. It was autumn 2009 before all the delays with the funders were sorted out and the project could begin in earnest. By this time, Dame Evelyn Glennie had already agreed to come and demonstrate the instrument at an opening on 19th August this year, so all the delays in getting started simply meant we had to work faster. Geologist Dr Rebecca Hildyard joined the team in Leeds to help source rocks, characterise them and then prepare educational materials for the display and for the web site:
www.ruskinrocks.org.uk.
Why do rocks ring?
One of the most satisfying aspects of using Cumbria for musical outreach is the diversity of rock types that ring. There are igneous, metamorphic and sedimentary examples, and so children can be introduced to the rudiments of geology along the way. What all the ringing rocks have in common is a very tight grain boundary structure, either with a very low porosity or with any pores completely isolated. However as well as these intrinsic characteristics, any piece of rock must also be free of hairline cracks. Sometimes blocks of ringing rocks in the quarry would yield sawn bars that responded with a dull thud when hit. And if you were very lucky, dropping the bar on the floor would make it break, yielding two short bars that rang!
Such was the diversity of ringing rocks that we decided to make an instrument with 4 octaves, each from a different rock type, and then add a smaller electronic lithophone with 12 keys, each made of a different rock type. We used Carboniferous Limestone (some beautiful notes, but very fragile), Borrowdale Volcanic Group slate and Shap Blue Hornfels, as well as the classic Skiddaw Hornfels, for the main instrument, with a range of additional Limestones and Borrowdale rocks in the electronic keyboard (christened the iRock when Kia promised to make it interactive).
After the initial cutting and polishing of the blocks of rock into bars, the detailed tuning of them into keys was done in Leeds, where Kia set up a musical workshop alongside a rock saw. For each rock he could predict the dimensions needed for a particular note within a few mm, but then they had to be hand tuned; the final tuning involved just polishing off a few tens of microns at a time. After several weeks of working round the clock, the 4 octaves were tuned to concert standard, and then holes had to be drilled in exactly the right place to allow the mounting brackets to be fitted. Meanwhile an instrument frame was being constructed by Marcus DeMowbray, which would be flexible enough to take a range of key sizes.
iRock
The main instrument we built is unique and incorporates a whole range of innovative design features developed by Kia, but from a geological standpoint, it is the iRock that is the most fun. Not only are the keys wired up so that you can generate different electronic sound effects from them using a keypad controller, there is also a large screen wired in. When a key is struck, the screen displays an image representing the vibrations on one side, but information about the rock that the key is made of on the other. This may be a picture of the quarry, or a thin section image, as well as the rock name and locality. Play the instrument slowly, and a roll call of Cumbrian quarries passes before your eyes. Play them fast and it is just a blur! This aspect of the technology has, I think, much wider potential for getting across basic information about rocks (and other hittable objects). At the moment, kids find it more fun to play a tune / make a noise on the iRock than to read all the screens, but I am sure someone will come up with ways to even up the balance.
After all sorts of hassles, and a lot of hard work, the instruments were assembled in a marquee on a field by Coniston Water at Brantwood a full day before the launch demonstration by Evelyn Glennie, who was even able to try them out in advance. The rain held off and people arrived in their scores. There is no doubt that appearing on stage with Dame Evelyn will be one of the highlights of my academic career, as well as one of the more fraudulent moments. You can catch a few minutes of her demonstration
here, and a longer video
here. But much better, if you are in the vicinity of Coniston, drop into Brantwood and you can go and play the instruments yourself.