This directory contains the schematic and board layout for the predecessor/prototype of the MIDI Patchbay Shield for the Arduino MEGA 2560.
This is a simple 4 MIDI IN / 4 MIDI OUT merger and splitter.
The MIDI Patchbay Shield is the newer design with more functionality, but if you want something simple and slightly easier/cheaper/quicker to build then this might be the droids you're looking for.