This is a Yamaha XG card, the SW60XG to be exact. It’s an audio card for a PC which extends the MIDI standard to include over six hundred instruments. By today’s standards the almost twenty year old card isn’t all that powerful, but it is interesting to see it used as a standalone device.
[Benji Kimba] posted the video overview of his project which you can watch after the break. The image above is found at about 2:35 seconds and about twenty seconds later you get a look at how he patched into the conductors on the edge connector on both sides followed by the MIDI in and out connections. Finally, we get a look at a proper schematic at the four minute mark which details the pull-up resistors, hardware reset circuit, and the optoisolator he added for the MIDI connections themselves.