@Autumn Brushtail
thanks! I did experiment with 30xx, both 3000 and 3001 settings, but even that seemed inconsistent even before vgm export. So the problem is some instruments seem to produce a kind of DC offset spike, or "click" when changing to a new instrument. The best "fix" I found for this is to play a different instrument at 0 volume before the new instrument starts. Which instrument works for this changes depending on the previous instrument, not exactly sure why, maybe something to do with which algorithm it's using. I just used trial and error to find which ones worked. I imagine with MML you could do something like that ~1ms before the new instrument, in order to squeeze it into a single channel.