I agree with what's been said. This box started out as one of those white breadboards and two pots. Then one encoder was added. Then I wired up the first perf board proto. It had an audio shield strapped on a Teensy, with 3 buttons and 3 pots. It was electrically identical to the board used in the audio library examples so that I could do all of those experiments to learn this stuff.
Then I added more pots, three encoders and Jacks for CV and gate inputs. All of these were added one or two at a time, then the code was written and tested before going further.
Once all of that was working I decided to make the jump to lots of pots. In my case 48 pots, 4 encoders, and analog CV and gate inputs. The black chips are 8 to 1 muxes. They get 48 pots into 6 inputs and require 3 outputs to drive them. I made 4 VCO's, two VCF's two ADSR's and all the mixers needed to make a stereo synthesizer into a T3.2. Later on I rebuilt the main board to work with a T3.2 or a T3.6.
There has been some discussion of the "controller" and its 32 inputs with 24 pots per channel. I believe that it's doable, and probably best done as 8 X 4 channel boards running through a USB hub.
I assume that this must control a "real" mixer somewhere, probably in a DAW like Ableton Live or FL studio. Some serious consideration must be given as to how you are going to get 32 analog signals INTO the PC for the DAW to work with, and the processing power needed to handle 32 audio streams while doing all the typical DAW stuff, like running several soft synths. This is not an easy or cheap task, and again can best be broken up into small tasks. My old setup used a pair of very old M-Audio Delta 1010 boards, each with 8 channels in and out. It has been working great for 10 years, but it requires a PCI slot (NOT PCIe). New PC's do not have PCI, and Windows 10 does not support it. I have recently switched to a Focusrite USB 8 channel box with outboard 8 input analog mixers on two of the channels to mix the outputs of my synths.
Again you can build one channel strip out of the 4 and get it all to work with the DAW or whatever you intend to control before going further. It would also be wise to keep a look out for used analog mixers. I have seen several for sale cheap now that the trend favors the new $$$$ digital stuff. I got a 32 channel Mackie for $100 at a ham radio show a couple of years ago. I haven't decided yet whether to rebuild it or gut it and use the pots for a controller like what you want to build.
One more thing. I used 1 meg pots for my synth because I had a bunch. A value this high can lead to inaccuracies when muxing them all because of the input capacitance of the A/D converters. I changed to 10K pots and simply wired all of them to the 3.3 volt output on the Teensy. Each 10K pot eats 1/3 of a milliamp, so there is enough current for a lot of them.