As per the original topic, the game is missing one third of it's intended music, namely that for the Rimtech faction, included on the first of the original game's two discs.

Any sort of solution that reinstates this missing music would be acceptable, but as that has not happened as of yet I am 'reopening' the topic that was incorrectly marked as solved by starting this one.

Are there any news about this ?

Afraid not :(

Ah, that's sad :S
I hope someone will at least find a fix/workaround...

Guys, there's a software named _inmm (exactly like that, with initial underline), it may help. With it I managed to make music properly playing in Heretic II, with dynamic music change and so on.

I'll make some experiments when I'll have some spare time.

EDIT: here is the full gamerip OST in both MP3 and OGG formats

https://downloads.khinsider.com/game-soundtracks/album/metal-fatigue-windows-gamerip-2000

Well, _inmm is already implemented in GOG Metal Fatigue installation so it has nothing to do with incorrect music playing.

So it seems that the only solution so far is indeed the "swap folder" method described here already as well as on Metal Fatigue forum on Steam.

So I made three separate music folders named MUSIC (yes, I do know that Neuropa music is played correctly because of numeration of files but I decided to make it separate as well just for convenience and to avoid confusion) to replace them depending on what faction I play at the time.