I'm using my Korg Extreme (midi from the OUT) going to midi IN on a Presonus 44VSL interface. This alows me to record using everything about the Korg as it is, or, also as a controller for everything there is in the 'instruments' section of my Studio One 2 DAW. It is quite convenient. Is it possible to add another workstation into the mix to act exactly as the first keyboard does? How & where to connect the midi cables- Or the next best scenario?
With a single MIDI input port, the 44VSL can handle only one device.
Nowadays, it is likely that a keyboard has built-in USB. If not, you can use a USB/MIDI interface cable to get a second MIDI IN.