The Matrix controller will have to feature 62 rotary knobs / potmeters so I will need to expand the number of analog input pins to "read" them all. To this end, i have designed an expansion board with eight CD4501 chips to multiplex a total of 64 extra analog input channels into one Arduino pin. This is the first circuit i've ever designed so I probably made loads of mistakes. Please leave a comment if you spot any! (I've already moved the 5V line away from GND)

Note that just a few wires have been drawn here for clarity