Regularly you shouldn't connect two output devices to one input device
without using a MIDI merge box.
Anyway, the receiving MIDI equipment might be able to handle successive
note on events for the same note number, while they were received
without note off events between those notes, but it's not good to send
no note off events, resp. note on events withe a velocity value of 0.
Drumsamplers and monophonic synth might be able to handle this, but for
polyphonic synth you could run into trouble.
> And there's no way in the world that missing note-offs could be added in,