This is my latest creation (made on 24 Nov 2015).
This began as an idea for a ridiculously lofi spring reverb. It's more like an amplified object playground. I like it because it can do many sounds (when used with my (amplified) diy bow and a couple of crocodile piezos). It works as a resonator/reverb (albeit with a very nonlinear amplifier and driver (the relay). A sort of electroacoustique effect, (to quote Kevin Angboly). It can also be a kind of oscillator, with feedback. It's also a fun and flexible amplified object, when used without the relay. I've used it to acoustify an oscillating no input mixer, touching/holding the relay, damping it or the strings with champagne corks and rubber bands. etc
So far I've only used it with a separate mixer, but I might make some extra electronics for it (more gain, a simple mixer) for standalone use. Probably not, though.
Here's a close up of the relay. I use the corks to prop up microphone, dampen the relay or strings, and more:
Close up of the electronics. The resistor is a 4,7k and the capacitor 1uf. The transistor is a BC517. Note the clever battery clip solution. This way, the battery won't lie on a table and tug on its wires. You can also half-unplug the battery and twist it, to turn the circuit off:
Here is the relayverb and noise bow next to each other. The noise bow can be used standalone, as a noise exciter for the strings (like a physical version of computer based physical modeling), to bang on things, to dampen the strings, and much else:
see also: Relays