I love this soundtrack by Mark Morgan; it's oozing with atmosphere and dread, perfect for wandering the post-nuclear wasteland. It's no wonder the original Fallout became a cult-classic..the game and it's soundtrack are wholly unique.
When it comes to the individual tracks, there are nice little flourishes and effects in each of them: from the alarms blaring in the background in "The Vats" to the sounds of crumbling stone and steel in "Junktown". "Caverns" sounds almost like an alien world, hinting of a new world filled with mutants and bizarre creatures.
The game has gotten a high-res version on Steam, which is sadly basically unplayable because of the UI not scaling with higher resolutions. I'll always prefer the classic, lower res version (although there are plenty of mods and hacks that might improve your experience).