It turns out that the Soundscape VIVO Windows installer does include a part that installs the DOS drivers into the C:\SNDSCAPE directory. The contents of this directory are slightly different from the SNDSCAPE directory for the other Soundscape models.
Eventually, I was able to manually configure the settings for the card in Windows to defaults settings (port 330, IRQ 9, etc.). I could then load DOS games (Descent, Duke 3D) from Windows and get GM music.
However, Windows would never remember these settings and would show a hardware conflict in Device Manager upon the next reboot.
In DOS, the TSR that is loaded is called SSINIT, and it is only 0.7K in size. It loads when you run the INITSS.BAT.
However, the MIDI in DOS is terribly garbled, nothing at all like loading from Windows. Not sure what is wrong--maybe something with the WavePort or OttoPort addresses. Also not sure if it is worth spending much more time to diagnose.