The E-66 has a GS-compliant sound module built into the unit, so you can use that for MIDI output, with the appropriate USB-MIDI cable. It also has speakers, so you can use the unit for audio output as well. The module in the E-66 is close to the Roland SD/SC-series modules of the time, specifically the SC-50/SC-33 and SD-35.

Not saying that might not be fun and/or educational, but you're heading for a very deep and complex rabbit hole there, bro.

If it's merely about results:
https://www.serdashop.com/S2P

Thank you for your replies! I am glad to hear that my E-66 will work. It would be a weird setup for gaming, but it will save me a lot of money for now. Besides, it is my favorite instrument I own: it sounds great. About compatibility: I see you say "GS-compliant sound module". Does that mean that not just any MIDI arranger will work? I see for example a lot of Roland RA-30, RA-50, RA-90 for sale and many others, also from different brands. The RA-30 is the only one that is actually pretty cheap though. What do I need to look for to ensure compatibility?

I have contacted the guy behind Serdashop before about audio for my laptop, specifically about the OPL2LPT. The problem is the games I intend to play, which are Windows games. He said there is no Windows 9x driver for the OPL2LPT. Before I purchased the ESS PC-MIDI 1/4 I saw actually looking at the S2P, but since there was no mention of a Windows driver, I lost interest.

Ouch man, as said by Cuttoon, that's quite a rabbit hole you're diving into.

Here's a good and actually pretty exhaustive (edit: brain fart) overview of the pre-2000 game midi jungle: https://www.retrobee.net/blog/midi-module-buy … or-retro-gaming

If you want your games to sound like the composers wanted them to sound, up to early 90's the MT-32 was king (and the CM-32L and CM-64, as they feature the same LA synthesis + a bit more, but it's almost anecdotal and only concerns a handful of games and probably out of scope this early).

According to Great Hierophant's blog Nerdly Pleasures (awesome resource), the RA-50 can actually work like an MT-32 using SoftMPU: https://nerdlypleasures.blogspot.com/2017/12/ … -emulation.html
Never heard it though so no idea if it's really perfectly accurate. And no idea about the RA-30 and 90.

Later in the 90's, it was all about the SC-55. There were the original SC-55, and a later release labeled mkII. More info there, again at Nerdly Pleasures:
https://nerdlypleasures.blogspot.com/2013/06/ … gs-devices.html

The SC-50 is basically a budget version of the SC-55mkII - it has no MT-32 compatibility patches, and only 1 midi input (which is fine for retrogaming). According to RetroGamer4Ever, your E-66 should be close to a SC-50, so that should definitely be a great way to get started for GS/GM games.

General MIDI being a standard, all GM expanders will work in the sense that they'll output music that shouldn't be too far off, for GM supporting games. They will vary in instrument patches, which are pretty hit and miss. Well known modules are the Yamaha MU series (50 and 80) and the Korg NS5R. I own both, and while they have they have their novelty charm and can actually sound great with some games, I usually end up using a Roland Sound Canvas module instead. Basically all of games were developed with Roland's devices in mind, so even if they don't sound "the best", at least you're pretty sure to hear it as it was meant to be heard.

I'd suggest to try to get your E-66 working, you already have it, and it will let you figure out how to get MIDI out of your computer. Once that's working and if not convenient and/or good enough for the games you want to play, you can look into buying different modules.

Hope I was somewhat clear and hopefully I didn't get stuff wrong but no doubt I'll be corrected soon enough if that's the case 😁
As said, it's quite a complex topic where everything you touch turns into its own can of worms.

Found that one about the RA devices in the meantime, interesting read:

Roland RA-50, RA-90 and RA-95 doubts about purchase or not

So, you can turn a RA-50 into a MT-32 with a hardware mod, or SoftMPU. But that's the only RA device that would work. TIL.

I also realize I haven't really touched on modern alternatives such as the MT32-pi. Oh well. Can of worms I tell you...

Thank you so much for your elaborate reply. I think I have a better understanding of how MIDI for gaming works now. I have enough information to get started. I am looking forward to seeing the amazing sound results coming out of a 486 laptop. 😀