I need to began by emphasizing that this is not entirely my original project. I began by looking for information about the chip and while doing that, I encountered a blog post written by someone who already made similar project. There was just everything I needed - not just technical documentation of the IC, but also PCB designs. I really do not like to reinvent the wheel when it is not necessary, so I after examining it I decided to replicate the main board. Unfortunately original site went offline soon after, but you can still access it using Wayback Machine.
The rest was relatively easy. Etching and soldering the PCB, mounting it inside enclosure and wiring. A lot of wiring. Regarding controllers, I decided to take another approach than author of the original project. I decided not to use tiny PCBs to hold potentiometers and push buttons. I used small plastic boxes instead. They fit well into a hand, providing decent level of comfort during play sessions.