I've created a modified version of SoftMPU that supports serial MIDI playback via the parasitically-powered MIDIMAN Portman PC/S. Yay.

The PC/S configuration supplants that of 38400bps-rate serial devices. Initialization is the same:

SOFTMPU.EXE /MPU:330 /OUTPUT:COMx (where 'x' is the COM port the PC/S is attached to)