Arduino to mix both analog and digital signals

[SPoT_D]

Hi all,

I was asked to make an arduino based pedal that actually uses simple arduino programming language to manipulate sound. This to make it a bit simpler to program than for example the ElectroSmash pedalshield. Something for a kid to have fun with without needing a degree in software engineering 
Took some research, but with the Arduino MKRZERO and some help from a little library to get a faster sampling rate i managed to get a pretty decent  fuzz, reverb and delay. (thanks to Albert van Dalen @ https://www.avdweb.nl/arduino/adc-dac/fast-10-bit-adc)

Now I'm looking to manipulate an analog signal for tremolo, vibrato, attack/decay kind of things and to make it possible for the arduino to mix both analog and digitally manipulated signal for wet/dry control
Does anyone have a good example of a circuit where an arduino regulates the volume  of an analog signal?
What would be the best way to go about this without using a digipot (which I think will mess with the sample rate too much, but correct me if i'm wrong)
Is there a JFET or a vactrol kind of approach? (I have both, but my knowledge of how to implement those are limited)

A schematic of a similar approach would be great.

Thanks!

[anotherjim]

PWM control a Vactrol would be conceptually easy. It has the advantage that the circuit you are controlling can be electrically isolated from the digital control and the time response of the LDR in the Vactrol is slow enough to filter out the PWM pulses.

[SPoT_D]

OK, I'll expiriment with a vactrol. Do I put it in the signal path or to ground? (kind of new to vactrol). Some ideas on how to mix two signals are quite welcome as well