From the MAKE Flickr pool

Barrie Sutcliffe’s installation titled The Small Within the Great consists of wall mounted strings played via data derived from the quantum decay of radioactive metals –

Experimental stage running brushed DC motors controlled via PWM amplifiers connected to an Arduino. Data is fed to the computer from an Aware radiation monitor that is looking at Americium 241. Speed of motors is controlled by this data, the time at which they change is a short constant to keep things as level as possible.
All strings are the same gauge, therefore when tuned via equal temperament only string length changes. This explains the ginormous, 7-meter long G1 on the top, which was so big that it really only gave off weird noisy overtones instead.

See more of the project in his Flickr set.