This is a modification of a Minitel interface for Oric by Frédéric Taraud published in Théoric. With the help of Daniel Prieto, I added a MIDI interface and possibility to switch between the two. As a matter of fact, I never tested the Minitel part because I didn't need it but I did build the rest and it worked fine. For instance, I wrote a MIDI sequencer that turned my MT-32 into a beat box. :-)
Here's the schematic diagram. All '157 switches are shown in MIDI position and all discrete logic is 74LS.