Detector Charles was my first ever ‘electronic-instrument built’ attempt.
It was born back in 2008 and it is a prototype of an audio Electromagnetic Field detector.
Practically, it grabs the weird ultrasonic sounds that machinery like hard drives, computers, scanners etc. create, which are normally not audible to the human ear.
It’s impressive to use a laptop surface as an (invisible) instrument.
Enjoy the sample below, it is just the detector scanning a part of a laptop keyboard.