FluidSynth version

FluidSynth runtime version 2.4.3
Copyright (C) 2000-2025 Peter Hanappe and others.
Distributed under the LGPL license.
SoundFont(R) is a registered trademark of Creative Technology Ltd.

FluidSynth executable version 2.4.3
Sample type=double

Describe the bug

In the attached soundfont, the preset 000:035 bass with no fretle sounds too muddy when compared to Polyphone and SpessaSynth. Note that I've tested in 2.3.7 (before the filter stuff happened) and it still exhibits the same behavior. So I'm not sure if both polyphone and spessa are wrong, or is fluid the incorrect one here.

Expected behavior

Probably it should sound like polyphone does? Well, given that I (the soundfont creator) programmed this thing in polyphone, I would assume that the soundfont should sound the same as in the editor I made it in. Not that I'm sure Polyphone is the correct one, but generally sf creators intend the sound played in the editor to be the definitive version of the sound that should be played. So if it turns out that fluid is right, I'm making an issue on polyphone's repo (and fix my program because it sounds like polyphone right now)

Steps to reproduce

1. lightweight.sf2.zip
   Note: remove .zip, it's just a raw SF2 file.

2. run fluidsynth with the soundfont.

3. prog 0 35

4. noteon 0 60 127

5. Compare with polyphone and spessasynth. The attack & hold phases have a way muddier filter in fluid.

Additional context

I apologize for the preset names in this soundfont