Techniques for audio sampling gritstone - Listening Landscapes

As part of the Listening Landscapes project I collected several pieces of gritstone and shards of Sheffield pottery from the riverbed on the River Derwent to sample at home. Just as a side-note they were checked for caddisfly larvae etc. before hauling them out - as far as I know they weren’t home to anything!

I wanted to sample the gritstone because it’s part of the river ecosystem, but also because it’s of cultural significance. In preparation for the project I bought an old copy of Walt Unsworth’s book A Portrait of the River Derwent, which describes the inception of the climbing scene in the area (Derbyshire and Peak District). The geology of the area was ripe for climbing, much like its US counterpart Yosemite.

While recording at Padley Gorge, Dr Scott McKenzie from the Derbyshire Wildlife Trust also pointed out the remnants of huge gritstone wheels lying beside the river. They had been hewn from the rock there, destined for the cutlery works in Sheffield but abandoned due to imperfections. I like to imagine they were just too humongous and cumbersome and they just gave up try to drag them out of the gorge.

The gritstone is beautiful doesn’t resonate well. I tried using different ‘exciters’, drum sticks, metal rods, a kick drum beater, but the sounds produced were quite flat, a dull ‘dink’. Knocking the pieces together sounded slightly better but caused pieces to break off. Not ideal. I tried a contact mic (DIY and pictured below) and various types of microphone but nothing really felt right.

My last ditch attempt was to simply slide the pieces over each other. The sandpaper quality of the stone produces a rasp, which I could record in stereo passing from right to left. The entry level field recorder I use, set to the highest bitrate, still gives great results. This half second clip, slowed to 30 seconds or more, produces a fairly broad spectrum rumble with lots of low frequencies. Pitched down several octaves, the sound immediately made me think of the cutlery works and the gritstone wheels. There’s something industrial about the noise, but also geological, as if you could record the sound of a glacier bulldozing its way through a landscape.