Braden Stadlman wrote in with a link to the Springatron 3000, a gigantic spring reverb made out of Slinky and cucumber:
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.
…Although it is very inconvenient as a reverb, it is very good for making horror sound effects by playing it with a violin bow.
This is just one of several DIY mechanical synths made by Nick of Nick’s World of Synthesizers.