GUS emulation volumes in Chocolate & PrB+ vs. ZDoom

I recently tried out the EAWPats patches in Chocolate Doom/Crispy Doom and I really like the sound of them (apart from some nasty guitars). BUT, the volumes don't seem to scale down properly at all. A good example is MAP08 of Doom 2, the guitar chords are supposed to echo. But with GUS patches, the volumes of the echoes are almost as loud as the main notes.

This is the same way in PrBoom+, but not in ZDoom, where the volumes decrease as they should.

Is there a fix for this? Is it a bug? Is it maybe just something lame with old Timidity or SDL?

Choco's GUS sound is described by Fraggle himself as "pseudo emulation" because really it's just feeding the DMXGUS lump to TiMidity.

ZDoom, on the other hand, is much closer to actual GUS emulation because Randy tweaked the TiMidity code using the Ultrasound MIDI driver's source code as a reference. The most salient differences can be found by grepping through ZDoom's source code for references to midi_timiditylike as they mark places where GUS-like behavior or TiMidity-like behavior is optioned depending on that variable.

Oh, so it probably is Timidity at fault. In fact supplying a timidity.cfg to "Native MIDI" also has the same volume problems. That's not so good.

I'm no expert on MIDI, but it sounds like Timidity (or whatever the culprit is) is treating note velocity as a linear volume scale. This is definitely incorrect; velocity ranges from 0-127, and a velocity of 111 is about half the volume of 127 when played through a typical GM synth.

edit: Indeed it looks like a lot of the ZDoom changes have to do with volume levels.

Yeah, this is an SDL_Mixer problem. It turns D_E2M8 into pure hell. on OS X it's even worse. it throws pitch bends into the strings of the doom 2 intro music.