Here is a non-electronic relaxation oscillator:

Overhand knot in a strip of carbon-loaded paper becomes an FSR that can be easily connected to your favorite microcontroller (in this case a teensy running with the Arduino C++ tool chain).

This is part of my Fingerphone instrument.

Not my first publication, but my first one with some challenging engineering. I did this in my late teens and it was published in a hobby electronics magazine, "Electronics Australia". https://www.adrianfreed.com/audio-oscillator-using-digital-ics

I discovered by accident that some folk from Greece published the same ideas in a professional technical journal in 1989 (attached). If you are a scholar of such things it is interesting to compare and contrast the modes of articulation in my vernacular engineering approach with those of the academic paper.

Experimental surface sensing for fingerstyle players

Novel and Forgotten Current-steering Techniques for Resistive Multitouch, Duotouch, and Polytouch Position Sensing with Pressure, Freed, Adrian , NIME 2009, 2009, (2009)

My table at Maker Faire 2007 including my first e-textile work with peizoresistive fabric, and my duotouch pad and floor sensors.

In 2016 I made the video below of a tear-down of those e-textiles with Hannah Perner Wilson.

Our Maker Faire table also include some great interactive demos whipped together by Andy Schmeder.

Michael Zbyszynski dropped in and talked about his Ikea bowl speakers.

It was great that Dan Overholt was nearby demonstrating his e-field sensor array.