sonicsidewinder: Aye, I tried.
I've narrowed down the issue as much as I can.
Skipping the Tombeng file transfers, I can copy over the tomb3dfx.exe, tombub.exe and Data folder; then delete the tomb.exe, then change tomb3dfx.exe to 'tomb.exe', and the game will still run fine on clicking the GOG-made desktop shortcut. (without the music of course, but it will run).
The issue is with these Tombeng files. It seems to not like me deleting the GAME.DAT file and replacing it with this renamed .cue file. DOS-BOX will just cut out.
There's gotta be a way to say...transfer the data from the tombeng.dat file and just plonk it into the GAME.GOG file.
In fact...shouldn't GOG be doing this seeing as an important fix has been located?
What could it be? It's highly unfair
I actually had this same problem earlier today and was struggling with it as well. I found out that the issue was that changing the name of tombeng.cue to game.dat wasn't doing me any good because it was staying a .cue file (it was just NAMED game.dat). So I fixed it by opening the file in notepad, going to file, clicking "Save As" (make sure the "Save as type" section says All Files instead of Text Documents) and saving it as game.dat. That changed it into an actual .dat file and the game worked with music and all.
Try it out, hope it works for you. :)