Lol. I know this is necroposting in general, but since there isn't a patch to this, I thought I could post some snippets here that can fix the BGS-playing problem...
Highlight all of the code in lines 127-129, and replace it with this modified snippet.
def bgs_play(filename, volume=100, pitch=100, pos=0)
volume = self.volBGS * volume.to_f / 100
hzm_Vol_Audio_bgs_play(filename, volume, pitch, pos)
Hit enter after line 213 of the code, and paste this in there.
now = RPG::BGS.last
Audio.bgs_play('Audio/BGS/' + now.name, now.volume, now.pitch, now.pos) if now
Or you could just take the easy way out and download the text file for a simple copy-and-paste overwrite.
Volume Control Patched.txt
In any case, thanks for the script translation Elemental Crisis. And thanks Kal, for the graphical bars modification. This makes for a neat little addition to my project.