You can use the OPTIONS > Save Default Synths which fixes a particular synth to an Output Port number. Very useful for GM based synths but not to those synths where you are required to designate the patches for each sequence. GM synths assign patches according the track settings for Program, Bank and LSB and therefore do not need to save the previous setups.

DXi and VSTi plugins use port numbers 17 to 32 and output through the host. Internal or external synths use Port Numbers 1 to 16 and output via their respective drivers according to their numbered positions in the MIDI Driver DISPLAY.