CAUTION: Please note that I do not take any responsibility or liability for any damage or mulfunction caused through this page. To modify or bend any circuits is all at your own risk.
1. open the housing of volca modular enclosure and unplug the power connector. it's easier to work if you also detach the speaker terminals.
2. drill a Φ6mm hole in the bottom of the housing. this is very severe, so you should ask your buyer (USBtribe) to share the guide PDF. pin jack has a diameter of about Φ8mm, so it's recommended to further shave the pin jack to fit after drilling holes in the housing.
3. attach the PCB of the MIDIModular so that it overlaps the TX OUT of volca modular. this PCB doesn't have good contact, so you should check carefully that the MIDI IN/OUT works properly.
4. close the housing. it's difficult to store the housing properly; be very careful not to damage the PCB of the volca modular.
5. ok, volca modular now controls both MIDI IN and OUT, making it very convenient to use.