Scratchy - HDD discs hacked into pseudo-turntables to alter sound(s) playing through WebAudioAPI on a connected laptop

For capacitive sense, maybe check out: http://www.espruino.com/STM32+Peripheral­s

There's code at the bottom specifically for capacitive sense on the Pico :)

For rotation, I'd maybe look at rotation encoders. While digital, you can get some with a relatively high precision (you could even use an old ball-based mouse).

Actually come to think of it, why not just dismantle an optical mouse and point it at the under side of the turntable? You'd have to do some poking around, but you can read the movement back pretty easily if you've got a mouse with the right type of sensor - some of them are USB only, but I think most of the cheap wireless ones are usable.

There's a library for the ADNS5050 - because you can use it as a camera - but actually plenty of other sensors use exactly the same protocol, just without the camera bit implemented.