I got some good info at the following webpage. This is generic info on setting up a soundcard for those who were not weened on DOS: http://dosmame.mameworld.info/index.php/Setti … _DOS_Soundcards

To get an onboard midi port working under DOS I think you just need to point DOS in the direction of the number assigned to the midi port in the motherboard's bios. The default port number for most soundcards midi port's tends to be 330. So if you set the onboard midi port to 330, you may get a conflict between the soundcard's midi port, and the onboard midi port, when trying to output midi signals. If your bios allows, a number other than 330 should be assigned to the onboard midi port, such as 300. You just need to then point DOS to this port number instead of 330, in the autoexec.bat.

Line in AUTOEXEC.BAT:

SET BLASTER=A220 I5 D1 T4 P300

Where:
A220 is the I/O Port address of the soundcard (e.g, SB Live! PCI)
I5 is the IRQ or Interrupt number of the soundcard
D1 is the DMA IRQ number of the soundcard
T4 is the Soundblaster type (or emulation mode)
P300 is the midi port you wish DOS to send midi signals to...

The only issue that may arise here is that some games, most namely Sierra ones, insist on sending midi signals to port 330. In this case you can use SIERRA MIDI PORT CHANGER, found here:

http://www.queststudios.com/quest/Utilities.html

Please let me know if I have erred in any of this.