XG uses GM as its' base, so it depends what samples are in the soundfont. Sounds like it could be just about anything. Feel free to upload the soundfont either here or elsewhere if it's big, and I will give it a listen. I've owned a few XG synths in my time.

MIDI support should be as simple as installing CoolSoft VirtualMIDISynth, loading a soundfont and using the program to select whatever MIDI device you want to use, whether the soundfont or something else (like MUNT for MT-32, for example). DOSBox should use it automatically.

I would recommend a soundfont based on the Roland Sound Canvas, because the SC-55 was used to compose most GM games and was the industry standard for a long time.
The one I am currently using is: Roland Sc 55 V1.1 Full Pack.sf2 (Google for it).

Spikey wrote:

XG uses GM as its' base, so it depends what samples are in the soundfont. Sounds like it could be just about anything. Feel free to upload the soundfont either here or elsewhere if it's big, and I will give it a listen. I've owned a few XG synths in my time.

Can I legally do that? Both my friend and I at least have had legal copies of S-YXG50 complete with a little official certificate (I still have mine around somewhere, lol,) which Yamaha felt some odd need to include with it so I haven't fretted too much about that even if Yamaha actually cared about MIDI (which they obviously don't) but I don't know if it can be uploaded on a public forum. Just that friend is on a newer Windows that has really crappy almost non-existent MIDI support. I mean, I wouldn't mind providing it and it sounds like you've as much legal right to it as anyone does, just it seems like it would be against forum rules since it's not really public domain or anything of the sort.

As the soundfont is based on the XG tables, you might guess it's approximately 4MiB. Actually, slightly less. I'm hoping it's because of more (hopefully lossless?) compression involved in the SF2 format or something, but maybe it's based on the 2MiB tables (if so there's a significant overhead though since it's 3.67.) Size is a non-issue.

MIDI support should be as simple as installing CoolSoft VirtualMIDISynth, loading a soundfont and using the program to select whatever MIDI device you want to use, whether the soundfont or something else (like MUNT for MT-32, for example). DOSBox should use it automatically.

The problem lies in how Windows itself handles it. No longer does it have a proper system providing a MIDI mapper or etc with you even being able to set a default (in fact, they entirely removed the entire section to select anything in 7 on up. Actually, I think it was removed with Vista.) In 7 you can set it via registry or using a tool such as the one the VSTi MIDI driver software provides built in to its configuration, but on 8/8.1 as far as I can tell you can't really set a true default. Rather MS expected you to manually select it within each program, assuming anyone sill using MIDI probably only has one or two trackers or doesn't even know enough about it to care about how awful their built in fake Roland synth really is (but they still know that one thing sounds better than another and still like the better sounding thing if you give them a real option.) Unfortunately, this is a bit complicated with DOSBox (especially identifying the right one in the first place without even a menu and I'd have to explain it to them over the Internet without hearing what they hear) and I don't know if I can ask them to do that part. (I'm setting things up and sending it to them ready-made to work and while I may have to talk them through an install or two, for the most part they know DOS commands ironically enough, but actually messing with dosbox.conf is probably more than I can ask them to do.)

I would recommend a soundfont based on the Roland Sound Canvas, because the SC-55 was used to compose most GM games and was the industry standard for a long time.
The one I am currently using is: Roland Sc 55 V1.1 Full Pack.sf2 (Google for it).

Well, that might work as a last resort -- though the SGM-V2.01.sf2 so many people use really isn't bad per se so probably would work if I can't get this to do at all -- but I've heard that soundfont and things like it before and honestly I just really feel like XG just sounds so much better for whatever reason. It just feels more overall balanced for generic use and overall sounded better (to my ears at least) in most games. As they never actually had a SC-55 (or even stuff like a MT-32 or whatever) I don't really think nostalgia or anything like that is a factor there. (Now, once you add soundfonts and DLS to the mix it's a different story, but the idea here is to set it up complete with one thing that "just works" where they won't have to change anything later. So while various soundfonts may be better at various different games, I feel like XG mostly just works right out of the box enough that it can be set and left alone.)

Honestly, I really think all emulators or interpreters like DOSBox, ScummVM, and etc should start integrating more actual MIDI synthesizer emulation functionality built in (in the main branch, not just third party builds.) Modern systems grow further and further away from anything remotely resembling proper MIDI support and even in Linux it's a lot harder than it used to be -- nevermind Windows with MS removing any sort of control mechanisms related to MIDI from the latest... (Can you even do anything like that VSTi plugin for Linux? I kind of doubt it.) It's getting harder and harder to get proper MIDI synthesizer support out of these things for anything more complex than either Adlib emulation or honestly not so well implemented software SB Live style implementations. It's sad that there are so few MIDI device emulators out there and that the DB50XG seems to be forgotten.