I can see a User had this same problem in May: https://retropie.org.uk/forum/topic/25809/is-ogg-music-file-support-broken-in-lr-tyrquake/2
I have put the music files in the correct place so far as I can tell.
This is what the retropie guide says:
id1/
├── pak0.pak ## shareware data
├── pak1.pak ## registered data
├── s0.sav
├── s1.sav
├── music/
│ ├── track02.ogg
│ ├── ...
│ └── track11.ogg
This is the structure that lr-tyrquake has set up, with two id1 directories.
id1/
├── pak0.pak ## shareware data
├── pak1.pak ## registered data
├── id1/
│ ├── config.cfg
│ ├── save files
│ └────music/
That is where I have the music placed currently but I have tried it in the other directories also. The permissions are 0777, and the format is .ogg as the guide states.
Any help appreciated.
Edit: I've got this working now, I have .ogg files and .MP3 files in home/pi/RetroPie/roms/ports/quake/id1/sound/cdtracks and they are picked up in Darkplaces.
I've also got lr-tyrquake working, the same files in home/pi/RetroPie/roms/ports/quake/id1/music
I don't know if the original .ogg files I had were bad, or if having the .MP3s in there makes a difference, but it is working whatever the problem was.