Some Turtle Beach sound cards used a software synthesizer that came with a 5 MB soundfont in ARL format (au30gm.arl, as an example filename). The ARL file seems to be pretty similar to the SF2 format. In fact, the file's comments section mentions that it is an "ASPEN specific SoundFont 2.0 bank".

I used Awave Studio and Viena in an attempt to convert the Aureal GM bank to SF2 format. Here is the SF2 bank: https://www.dropbox.com/s/xijfdstp5t56zvm/Tur … l%20GM.sf2?dl=0

It has GM melodic presets plus GS drumsets. I fixed some out-of-tune instruments, fixed the electric snare in the standard drumset (it seemed to have some kind of distortion), and improved the release of String Ensemble 1.

The soundfont could perhaps be further improved, but I'm not sure if that just ends up making it "less authentic".