This is basically a giant spring reverb made from 10 slinkys. I was trying to make the best sounding spring reverb possible, I think I achieved this but it is probably the most inconvenient spring reverb ever made. The reverb time (sustain) is so long that the springs need damping and I found that the best material for doing this is a slice of cucumber wedged under the end of each spring, other materials like foam or rubber tend to kill all the treble.

Link (with MP3 audio clips) – via Make