That project is on the Teensy site. I have asked a few questions but assume it uses the 16x1 mux to feed into a Teensy that has 10 ADC pins which would support all but the most ridiculously sized keyboards. He was getting a refresh rate of 1kHz on a 48 key keyboard (4 ADC pins scanning 4 off 1x16 mux) which is okay. Maybe a bit faster would be nice.