Simple Harmonic Motion - Fascinating to watch
Here is a YouTube Video that could be the basis of an inspiring idea - or maybe it already was! Be patient and watch through the variations.
via Kottke.org
There is an informative site about this working model here.
I found a similar construction on YouTube but the video is taken from an different angle. Still fascinating to watch.
David used the concept of viewing balls moving in three-dimensional space to create wave patterns in a kinetic sculpture piece back in 1990. The wave patterns emerged when you viewed it from one fixed spot. Symphony is from well before we had a website or video. We do have a still photograph so you'll have to use your imagination!
Symphony by David 1990