While not conventionally musical, the Electrochemical Synthesizer’s process for generating sound is unusually interesting –

Pressing a key causes salt solution to flow over a copper and aluminium connection generating a low signal which is filtered by a capacitor and then amplified, creating a complex white noise, with amazing fluctuating oscillations.

The device demonstrates how complexity can be generated using simple “analogue” and wet components.
The inspiration for the synthesiser came from the website “Peculiar sounds from Aluminium ” by Nyle Steiner.

Update: Here’s a vid with direct audio recording –