Hello everyone! =)

Say goodbye to "_inmm", something better and straight to the point awaits you...
A great solution to make the music play correctly: https://github.com/ayuanx/ogg-winmm

Unfortunately (or not) it only accepts files in ogg format, so if you have files in mp3 format on your side, use this to convert to ogg: https://www.ascensiongamedev.com/files/file/26-batch-mp3-to-ogg-converter/

These great tools have been tested on Heretic II and Driver (1999), they worked like a charm! They are simple to use and fulfill their purpose with excellence.

Best regards!

What is "_inmm" ? Why is/was that a problem?
In other words: I'd be glad if you could provide some context.

We don't do that here.

Dude, I didn't want to have to write a boring text here, but, in short, here it is: https://revolt.fandom.com/wiki/Inmm.dll

Look at the step-by-step and realize how boring it is to configure this hellish thing. One thing I don't like about this tool is that it forces you to patch the game's ".exe", and this is bad in many ways when you simply decide to get rid of _inmm, when "_inmmServ.exe" (I think that's the name) decides to stop working, preventing you from starting the game with the music, in other words, it's a tool that works arbitrarily. The only positive point is that it accepts more audio formats.

And just for the record, _inmm is a Japanese program, the guys' website is written in Japanese, and I'm not Japanese and don't understand the language at all, so the link there shows more or less how this devilish program works. I hope this has clarified things. =)

That didn't really tell us anything. But from what I can loosely glean from context is that it's a CD Audio emulator, which you could have spelled out from the description of the github repository.

Which is, I might helpfully point out, in English.

stares at screen.
well thats a handy lil guy.
but wait.. hasn't audio tracks been digitized into iso's years ago?
at least we can now use the useless list of mp3's that stagnate while or games sing in silence.

i remember when i was a kid i could not get a cd player for a good price.
took a creative cd drive, 12v power supply i made and a pair of desktop speakers, was dancing to prodigy from wipeout.

correct but you can convert mp3 to ogg

I'm assuming you don't know this: several GOG games use _inmm to emulate CD audio, the music itself. In fact, _inmm is mentioned extensively on several pages of PCGamingWiki, here are some examples:

https://www.pcgamingwiki.com/wiki/Heretic_II#Music_does_not_loop
https://www.pcgamingwiki.com/wiki/Driver#Music_does_not_loop
https://www.pcgamingwiki.com/wiki/Sega_Rally_Championship#CD_music_not_playing
https://www.pcgamingwiki.com/wiki/Sega_Rally_2#Issues_fixed
https://www.pcgamingwiki.com/wiki/The_House_of_the_Dead#Restoring_in-game_music
https://www.pcgamingwiki.com/wiki/Quake#Music_does_not_loop

These are well-known games, and I'm sure many people have visited these pages at least once. _inmm is basically the dgVoodoo of audio, just like dgV, inmm has been mentioned in various corners of the internet for years. It's strange that you don't know it.

Regarding "ogg-winmm" it would be redundant to write "emulator", considering that it's already written in the GitHub repository. :) Correct! But ripping the music from the CD is the first option, a second option is to download the files in mp3 format from a very good website, which unfortunately I can't mention the name due to copyright issues, etc. This reminds me 2001... When I would take my music CDs and play them on my good old PS1. My mom's house didn't have a music player, so the PS1 was my system to listen to my favorite rock and roll bands. XD

Of course, but that means sourcing your audio from elsewhere, and there are plenty of programs that can convert to OGG from whatever audio format.

flac would be more convenient for a CD-quality music. And even if you have only mp3 tracks, converting them to another lossy format will reduce their quality even further.

Well, most games from the 90s used the Ogg format for music, example: Quake II (the classic GOG version uses Ogg). In the early 2000s until the middle of the first decade, all games used MP3, examples: GTA 3, Vice City and even San Andreas (side note for SA, which was a DVD game). I mention these three because they had real songs, I mean licensed ones, and a lot of the content on their radio stations was, obviously, recorded in the studio.

I've never seen any old game playing music in FLAC format. Yeah, I know, some GOG releases come with soundtracks in FLAC, but this is not the standard format that the games run internally, as no CD/DVD came with this format, perhaps, there were some, which are rare exceptions. Regarding loss of quality, this only happens with the wrong tools.

...
Vorbis: Initial release May 8, 2000
Ogg: Initial release May 2003

Errr... After talking so much about Ogg, for a moment, I confused it with MIDI, a format introduced in the industry on February 1, 1983 (https://en.m.wikipedia.org/wiki/MIDI). I remember that Build engine games used this format, but for a moment I confused it with Ogg. Hell, there are so many formats and so many dates, that my single-core brain has trouble processing it. :)

MP3 was introduced after 1995, if I remember correctly in 1997 (https://en.m.wikipedia.org/wiki/MP3), and in 1998 was the appearance of the first portable MP3 players. Either way, the FLAC format didn't exist before 2001 (https://en.m.wikipedia.org/wiki/FLAC), so CDs from the 90s didn't use this format. Due to the popularization of the MP3, it kind of became the industry standard in the late 90s and early 2000s, and remained that way for many years.