On the software side capacitive touch sensors can be as simple as using an Arduino library for the purpose but [John] rolled his own code, so give it a peek.

Capacitive touch sensors are entirely in the domain of DIY, requiring little more than a carefully-chosen conductive surface ...

If you have a few hours spare and fancy creating a new Arduino project in your spare time you might be interested in this fun Arduino infrared touchscreen music controller which has been created ...