Sorry, been meaning to answer this after trying to hunt down some information and I haven't had time for the hunt, so I've ended up leaving it unanswered for ages. The main answer is that you probably can't. As far as I know, UB never had background music in any of it forms. The reason I was going to chase down some info, is that I have a vague recollection of looking into tricking background music into working with UB. It's such a long time ago, I just can't remember now. I imagine, if I had, it would of probably been under the old system where glidos recognised certain patterns of textures and used that to trigger sounds. That's long been superseeded by the updated TOMB.EXE binary which has all the triggers put back.

TR:UB doesn't have the audio tracks from the original TR. The reason for that is the gold was only released for PC version (not for PSX), which didn't have those tracks in the first place. Additional audio was only included on the PSX disc, so it was simply not used in the creation of the gold.

On a sidenote, you probably wonder WHY the hell would Core not include additional audio to the PC version, especially if the triggers are present in the levels. Well, back in the days, CD drives were still not perfect, and the game could freeze solid if the audio track changed from one to another. It was just easier to get rid of it than to face problems like that.

The Gold release of Tomb Raider has 3 audio tracks on the UB disc.

Yea, probably menu theme, Egypt wind background and Atlantis heartbeat.
No other soundtracks, just like it was on the PC version. They weren't used in the gold because they weren't included in the PC version. Well... pity really, since TR1 gold was released after TR2, and the drives were reliable. TR2 didn't have any removed tracks, so I guess the problems were gone by the time.

Paul, I wish you could re-enable the old texture-based audio support specifically for TRUB. I had started building such a pack seven years ago (gah!), and it worked reasonably well, although it was a huge pain to detect certain texture patterns. At least the background tracks played correctly.

When it was discovered the TR exe still contained the original triggers, the old code went the way of the dodo and I couldn't work on TRUB anymore.

Eeek! Yes, I can probably reenstate that. I'll have a look when I can find some time.

Note to self:

Audiopack revival