This is a video demo by pask present of an electrochemical synthesizer. The video features audio recorded direct out (rather than microphone and speaker/amp).
The sounds are produced by an electrochemical reaction between aluminum, copper and salt water (NaCl), fed through a pre-amp after basic filtering via a capacitor and resistor.
The originally inspiration for the electrochemical synthesizer was the webpage “Peculiar Sounds of Aluminium” by Nyle Steiner. home.earthlink.net/~lenyr/alsounds.htm