As seen in the element14 Presents video below, Dave Darko was printing a volcano model, while eating a giant plate of something resembling scrambled eggs, when he noticed that his printer was making a distinct sound that “means something.” When hearing automated machinery like this, one’s brain does seem to try to pick out patterns or even messages, and in this case it apparently leading into him building a model of the famous sound/light device from Close Encounters of the Third Kind.
Input for Darko’s rig is via a miniature keyboard, which pipes signals to the setup’s Arduino Micro. This activates a series of programmable LED strips, arranged to light up a 3D-printed and laser-cut 12 x 6 matrix diffuser. In addition to its MIDI input, it features a microphone as well. The Arduino does a FFT (fast Fourier transform) with this info and lights the appropriate LEDs accordingly. Although playing the Close Encounters tune would get old after a while, the matrix looks like a really excellent way to visualize sound, and it could be a fun unit to mount next to your stereo.
In MIDI mode, signals are also passed along to Darko’s computer that functions to actually play the sounds, as his keyboard (and presumably many other instruments) does not make noise when in MIDI mode. If you’d like to make your own, design files and a parts list are found here.