By Ella Raff, Researcher
The Museum recently installed Anita Chowdry’s Iron Genie sculpture in the Top Gallery. It is a modern reworking of the harmonograph, a 19th-century instrument that creates beautiful curves from the swing of pendulums. I’ve been working with the Iron Genie for nearly a month now, and despite our initial chemistry, I have hit a frustrating wall.
As visitors can see when they help to get the harmonograph running, one way of interpreting its beautiful pictures is as visualisations of particular sounds. Every musical sound has its own frequency; and in the same way, a pendulum swings with a certain frequency. The frequency of the pendulum is the same kind of frequency as in sound, only slowed down by about 1000 times to a level which we can see.
It is the frequency of the pendulum that takes charge of the kind of picture you get. We can alter the frequency of the pendulums by changing their lengths – so by moving the weights on the bottom of the pendulums up and down, we can set the Iron Genie up so it is creating pictures that represent a particular sound frequency.
Anita, who created the Iron Genie, sent me a wonderful book by Anthony Ashton, Harmonograph: A Visual Guide to the Mathematics of Music, which details the types of pictures you would expect to get from certain frequency ratios. For example, by putting just two of the pendulums in a frequency ratio of 3:2 (doing some actually not-so-fancy maths to get the length ratios) you would expect to get figures resembling flowers or stars. In musical terms, a frequency ratio of 3:2 represents a perfect fifth harmony.
Maybe this is selfish, but I would love to set the Iron Genie off and be able to predict what kind of picture we might get. At the moment, we are getting absolutely beautiful pictures, but I’m unsure exactly which musical harmonies they correspond to. It would be fantastic to clearly see what certain musical harmonies look like.
Unfortunately, as is so often the case, this perfect theoretical world doesn’t actually bear much resemblance to the real world. Although it is true that the length – and thus the frequency – of the pendulum is the main variable in changing the picture type, there are hundreds of others: the way you set the pendulums going, where you hold the pendulums, and the interaction between them. In one respect, this is great – every picture is totally unique, and there is a peculiar magic in the Genie’s endless creativity. However, it is totally frustrating as well!
I have spent the mornings, when the Museum is closed, fiddling around with the harmonograph to try to limit the variables that are interfering with my patterns. From slightly impromptu solutions (clamping a pendulum perfectly still with Blu-tac), to running around the Genie in manic circles to monitor the pendulums, to posting desperate pleas for ‘Anyone?’ on Facebook who might be able to help me, I am becoming mad in my quest.
Yet with some help from friends, I am beginning to make progress in predicting the kind of curve that will be produced by the pendulums. On the right are some of the pictures I’ve managed to produce from very simple harmonic ratios. They might not look very impressive but I am certainly getting closer.
To be continued… (unless the frustration kills me, in which case, know that I died trying).