This is code meant to run on a MaKey MaKey board. It uses capacitive sensing rather than the standard MaKey MaKey high resistance switching. With this technique, a person can touch an input to trigger it without being connected to ground. It's useful for things like musical paintings and posters, so that people can walk up to them and interact by touching a conductive region, without also touching a ground connection.
ericrosenbaum/makeymakey-capsense-keyboard
Capacitance sensing code, so your Makey Makey works without needing to connect to gound
Arduino