I can't say specifically whether this applies to Cubase Score, although I used to run a C-Lab Export (DB25 Serial Midi Expander) from the 9-pin Serial ports on the TT or MSTE - using Emagic Logic. I just used a standard DB9-DB25 cable, exactly the same kind that modems required, and it worked fine.
It was only a matter of finding which of the ports that the MIDI information was being sent to - which means, which port is the same as the serial port from the ST.
I believe that it is MODEM1 that you are looking for.
