Thanks to NewRisingSun's DosBox patch to log CMS/GameBlaster audio into VGM files, there is now a way to get some source material for experimenting.
So I wrote a simple program that can read the DosBox-dumped VGM file and understand barely enough of it to render some GameBlaster audio output to a file.
At first try it was just outputting garbage, but after fixing one stupid bug, try to guess the look on my face when I first heard this!
The flac file is post-processed in Audacity, it is resampled from 3.58MHz to 44.1kHz and then high-pass filtered to remove DC offset.
So the renderer does not (yet) output audio file that could be played normally.
Let me know what you think.
I was kind of hoping it would sound somewhat better though, but what can you expect from square waves, no matter how great they are resampled/processed.
Also, this made me realize that VGM file can't properly handle external triggering of envelope generators, but fortunately this music does not use envelope generators at all.