プレイヤーじゃないけれど出力するおと全ての音質を変えるやつで
Dynamic Range Compressorって自動音量調整の機能がある

JamesDSPManager
https://sourceforge.net/projects/jamesdspmanager/

https://a.fsdn.com/con/app/proj/jamesdspmanager/screenshots/ScreenshotMainApp1.png
https://a.fsdn.com/con/app/proj/jamesdspmanager/screenshots/ScreenshotMainApp2.png

Features
Equalizer
Linear phase bass boost
Convolver
Multi-mode reverb
Dynamic Range Compressor
Stereo Widen