(Actually not about the game at all, but about the msadp32.acm codec file)
Affected game: Warhammer 40,000: Chaos Gate (Classic)
AppID: 4280890

System Information

Short form, because it should be unrelated. Solution provided further down.
https://gist.github.com/DerFzgrld/eb2fe275319592062bf21fd36357685b
Any Proton Version (10.0-4 to name a stable version)

I confirm:

• [x] that I haven't found an existing compatibility report for this game.
• [x] that I have checked whether there are updates for my system available.

steam-4280890.log

Symptoms:

The game will have no ingame audio beyond cutscenes.

Cause/Solution:

The codec file msadp32.acm (compatibility data: windows/syswow64/msadp32.acm) is significantly different from the file actually included in Windows and overriding it with the Windows version does fix the issue on a per user basis.

Request:

Provide a working version of msadp32.acm with Proton.