OPL-3_FM_128M.sf2 is a soundfont (.sf2) that emulates the sound of an original OPL3 Yamaha YMF262 chip, which was the original sound that was produced when playing a MIDI file on older computers from the 90s.
This OPL3 Yamaha YMF262 chip was commonly found inside of machines that came with Windows 3.1, Windows 95, Windows 98 & Windows NT.
These chips were replaced with the newer Microsoft GS Wavetable Synth (Roland Virtual Sound Canvas).
The .sf2 file was created by Zandro Reveille, as far back as Jul 29, 2015. and was uploaded to Musical Artifacts, a website known for housing many .sf2 files.
The current & only version can be downloaded at Musical Artifacts.
Note: The .sf2 is in a .zip file! However, the .sf2 is the only file inside this .zip. This is a commonly used method to compress the file to a smaller size.
Possibly the closest you're going to get to replicating the original 90s midi sound produced by an OPL-3 chip without inserting a real OPL-3 chip inside your computer, getting Virtual PC (ew!) or DOSbox
In comparison to real OPL-3, it does sound slightly-less clear, but hey, it doesn't have that "distortion" that emulated OPL-3 on virtual PCs have (or in the case of Virtual PC, total distortion), so this may be the best replicated OPL-3 sound you can get!
Also, it works well with software that supports Fluidsynth (such as VLC Media Player), and does not have any out of tune instruments, or any instruments in the wrong patches.
If you want any midi file to have that classic OPL-3 sound, this soundfont is recommended!
Current Version - https://musical-artifacts.com/artifacts/15/OPL-3_FM_128M.zip
Musical Artifacts page about the .sf2 file - https://musical-artifacts.com/artifacts/15