Note: I can't share the specific MIDI file I was using as it's private, but in case it helps find the soundfont, here's a sample of ffplay playing onestop.mid from Windows ME. It sounds like chiptune at first, but after using the private MIDI file I can confirm that it isn't chiptune. The piano patch sounds kinda like an organ?
Here's a link to the onestop sample (Warning: it becomes ear grating after about 20 seconds due to ffplay misinterpreting percussion as notes; this is why I chose this specific song): https://files.catbox.moe/2ecdhq.mp3
This is what ffplay says when it plays onestop.mid: https://pastebin.com/SVuJai0H