Erica Synths has a series of educational modules for learning about electronic music generation. I’ll be doing all of them, and we started with their EDU oscillator, then did the envelope. Next is this one, their simple VCA . Even if you don’t buy the kit, I recommend you download the user manual, it’s a great practical guide to electronics in music.
Very serviceable dual VCA, if you need more this is a good choice, easy to build and inexpensive.
EDU VCA build
-- Ravenware
Good for Erica! Years ago, ARP had a series of separate boxed modules for the same general reason: teaching synthesis. You sort of see this with the Littlebits stuff as well. I applaud this, though...it might not be right for us old farts, but if you've got a kid or grandkid that's fascinated with sound and electronic tinkering, these are fantastic. Take it from someone who grew up with all sorts of electronic toys.