I am kinda surprised about someone catching on to these being soundfont-jobs, lol. What I used was an absolute whole hodgepodge of different ones I've downloaded across various sites over the last decade, and endlessly mixing and mastering the channels until I think they sound adequate. It would take a long time for me to look back and see the ones I've frequently used when originally developing
my late-2.1 music replacement mod these are sourced from, but things like "SGM", "Timbres Of Heaven", "Arachno Soundfont", some Yamaha SF2s, and a couple game soundfonts like a huge Spyro one, and Touhou... believe it or not.
Taking an opportunity to also say that the title screen music and Burning Caverns' music actually stem not from Emerald Quest, but another old fangame named "Sonic Legends",
no relation to the one on SFGHQ. These two musics were bundled with the Emerald Quest ones in a big MIDI music ZIP that their composer, Arrow, archived back then. Really thankful he did so, and even if S:EQ is a bygone fossil, it's gratifying to know he brought great music to SRB2 right from the beginning.