This little PK3 contains the bare minimum SNDINFO lumps that make GZDoom make use of the remix tracks which are inside the rerelease's extras.wad file. The tracks have the H_ prefix as opposed to the usual D_ so just loading extras.wad by itself won't do anything.
This was tested and works with Doom, Doom 2, TNT, and Plutonia IWADs.
This was also tested with the rerelease's masterlevels.wad, nerve.wad, and iddm1.wad PWADs.
Load order matters for these PWADs so make sure the PK3 is loaded after one of these. Use Doom2 as the IWAD.
Spoiler: More detailsEDIT: Removed old attachment "gzd-extras-sndinfos.pk3" - replaced with the "v2" version.