>>> I was wondering if that fixed the MIDI low volume problem that Apple has had since 10.6 ?
If anyone interested in helping to get this issue resolved,

I haven't noticed any problem. I just had a listen on Mountain Lion (10.8) and Snow Leopard (10.6.8).
If I understand the bug description correctly, the MIDI is supposed to be quieter on Mountain Lion, and this should affect all MIDI programs using the built-in Apple DLS synth.

But I just tested, and the MIDI volumes sound identical to me, both in absolute volume, and relative to the audio (RealDrums) in the song.

-I used a MIDI style (ZZJAZZ.sty), and had the drums replaced with RealDrums JazzBrushes#1
- so having a mix of RealDrums and MIDI would expose a bug, as we would hear the drums too loud on Mountain Lion.
But they sound the same to me.

Here are the audio renders:
Snow Leopard (10.6.8): http://nn.pgmusic.com/pgfiles/jazzu/misc/Snow_Leopard_ZZJAZZ.m4a

Mountain Lion (10.8.2): http://nn.pgmusic.com/pgfiles/jazzu/misc/MountainLion_ZZJAZZ.m4a

Here are the same two files in a ZIP http://nn.pgmusic.com/pgfiles/jazzu/misc/MountainLionAndSnowLeopard_BiabFiles.zip

These renders are of the demo song /Applications/Band-in-a-Box/Songs/ZZJAZZ.MG1
Volumes are flat at 90.
They have MIDI bass,piano, and trumpet melody. And RealDrums for audio.
If there is a bug, the Mountain Lion one should be sounding quieter, in relation to the drums.

Have Fun!
Peter Gannon
PG Music Inc.