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Searching for singing slate

This week’s blog post is an account of the difficulty encountered sourcing suitably resonant stone for use in the production of musical instruments. It should hopefully be of interest to those curious about resonant stone who are perhaps interested in producing their own instruments.

In 2015 as part of my undergraduate dissertation I produced a musical instrument called the Electromechanical Lithophone:


https://www.electromechanicalmusic.co.uk/lithophone.


This consisted of a two-octave lithophone and an electromechanical system designed to enable the instrument to perform autonomously. Sharing similarities with the xylophone and glockenspiel, the lithophone is a tuned percussion instrument with resonating bars that are made from stone rather than wood or metal.


As part of the project I had decided to attempt to produce my own resonating stone bars. The main challenge this presented was sourcing stone that was sufficiently resonant to form part of the instrument. Lithophones are not produced commercially and there was very little information regarding what specific types of stone tended to resonate.


Initial research had shown that several of the most well-regarded lithophones were produced from slate hornfels, sourced from Skiddaw in the Lake District. I began my search by visiting a local reclamation yard who had a considerable inventory of slate roofing tiles. Unfortunately, upon investigation it was found that whilst some of the tiles produced a somewhat perceivable pitch, none of them produced any notable sustain.


After further research I found that resonate slate tended to comprise of very dense stone with very tightly grown grains. The tighter the grains, the easier vibrations are able to travel from one grain to the next without losing energy.


Resonant Slate found in Aberllefenni.

Areas within North Wales and the Lake District were identified that were known to possess particularly dense slate, I contacted various quarries and slate mills to enquire about arranging a visit. Wincilate Slate Ltd. http://www.wincilate.co.uk/ are a company based in the old Aberllefenni Slate Quarries in the valley of the Afon Dulas, Wales. Aberllefenni was home to Foel Grochan which was the longest continually operated slate mine in the world until its closure in 2003. The slate extracted from the narrow vein in Aberllefenni is known to be especially hard and dense.

Wincilate kindly allowed me to spend a day searching through their vast storage yard in addition to the safe sections of the quarry. After searching through at least 30 types and thousands of pieces of slate I managed to find a single variety that produced a satisfactory resonant sustain. The staff at the slate mill informed me that the resonant variety was not local to Aberllefenni and was most likely a North Welsh green slate imported many years ago from another quarry.


I have carried out subsequent research to further establish why this particular stone resonates so freely compared to the other dense slate found at Aberllefenni but have yet to draw any quantifiable conclusions. In the future I plan to visit Skiddaw and search for stone examples from the surrounding landscape.

Electromechanical Lithophone at MOMA, Machynlleth. (2016)


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