Auto variable resistor - possible? How?

[SprinkleSpraycan]

I have been playing with different pt2399 designs and am wondering how to go about creating an auto-expression circuit to move the time pot for me as I play. I like the sound of placing an ldr between time pot and ground or across time pot lugs 1 & 3. But I'd like to have more control than casting a shadow over the ldr. 

Perhaps something envelope controlled based on the strength of my attack. Or lfo controlled so I can set parameters.

I think this is a pretty good idea.
https://oldbloodnoise.com/pedals/p/expression-ramper-hk
But where do I even start? I've browsed around but found nothing relevant except for maybe going down an arduino route. I'm hoping to stick to analog.

Thanks to anyone who can point me in the right direction. 

[ElectricDruid]

This project is pretty much exactly what you're talking about:

https://electricdruid.net/two-stomplfo-projects-ptwobble/

I think I've got a few PCBs for this if you're interested, so ping me a mesage. It's the LFO-controlled idea, not envelope-controlled, and it's based on my StompLFO PIC chip, so it's a microprocessor, but it's a programmed chip that you just use, so you don't have to mess around with Arduino programming stuff to make it work.

[Matthew Sanford]

Get the Druid chip, he has the OneShot also, same pin out for one off waves on demand. For a good crazy use with StompLFO, search Fideleater here, long thread to learn from.

For an analog choice, look at Jenny Greenteeth...must be Gen X, so many Jennifers...

[Aleph Null]

I have an envelope controlled delay design here.

Mad Bean makes a circuit that uses an optocoupler instead of a transistor in the Degenerator.

Dead Astronaut has an even simpler approach detailed in this thread.

It's also probably worthwhile to look into the Mid-Fi Electronics Clari(not).