ZDoom

You will want any MIDI player that uses system MIDI. This can include programs like Winamp, MegaMID, or TMIDI. I don't know where to find those nowadays, but Google would help you, I'm sure.

I use VanBasco's Karaoke Player to play MIDIS. It's the only MIDI player that cuts out the awkward silence at the start of some MIDIS and loops in a way that doesn't sound cringy and horrible.

I recommend using SoundFont MidiPlayer, it's really nice, you can choose any playing device you have there in the settings, and also play it with your custom sf2, setup fx and etc.

To use doom opl3 (as well as apogee) you must setup your genmidi bank files and name a desired one as GENMIDI.OP2 in the C:\OPLSynth\ directory

To set a default MIDI playback device in Windows Vista and higher, I recommend to use this application (shame to microsoft)

Although, these drivers aren't perfect but they still sound pretty good and exploit the most accurate on today Nuked OPL3 emulator.
Such a shame they can't play pitch bends correctly. Sound fonts will never replace a good OPL3 synth, sorry it will require large amounts of data to store that many samples to make it sound good, otherwise chipmunk effect is going to be presented.

Also: to use OPL3 mode of doom opl3 driver you must:
-Right click on your computer icon.
-Choose properties.
1. Advanced paramaters
2. Variable environments
3. Define a new virable environment
Create a DMXOPTION variable
Give it -opl3 flag and if you want -doom2

I have just tried Soundfont Midiplayer with the test MIDI I ususally use: A MIDI of "Do the Mario" From the Super Mario Bros. Super Show. I might still stick to VanBasco because this still has that looping problem I mentioned a couple days ago while VanBasco stops for about a second before looping.

EDIT: Sticking with Midiplayer.