Much of what I’ve said about The Fellowship of the Ring also applies here.
Yet there’s more “mood music” to The Two Towers, where you can queue up the music and just let it play in the background. Because, if you remember, there’s a lot scenes where people are just travelling from place-to-place, little combat or sudden surprises.
Overall, the music conveys a sense of urgency. Hurry up. Get moving.
For example, The Fellowship of the Ring is what you play for adventure likes The Sunless Citadel, or (even better) The Forge of Fury, then you would play The Two Towers soundtrack for lengthy Third Edition adventures like The Red Hand of Doom–which so happens to feature a massive orc invasion and lots of traveling by the characters.
Hurry up. Get moving. You’re running out of time.
You can pretty much play “The Riders of Rohan,” “The Passage of the Marshes,” “The Uruk-hai,” “The King of the Golden Hall,” and the “Black Gate is Closed,” in order, without interruption. Which is wonderful when you don’t want to break the mood.
The strange thing, tracks like “Helm’s Deep,” “The Hornburg,” and “Isengard Unleashed” might not be good combat music for your group. They’re almost too epic, composed for armies marching and clashing, instead of individuals fighting.
“Foundations of Stone” is great to play to start with an ominous tone to your session. If you remember, it played in the movie as the camera floated over the Misty Mountains and recap of what happened to Gandalf commenced.
I played this for my group, years ago, of course, at the start of the session after their characters had been captured by evil beastmen beneath the Dragonteeth Mountains in The Forest Oracle. (Yes, that Forest Oracle.) I had updated it to D&D 3e and made my own adjustments, though there were still quirky things about the module that I had overlooked.
Fortunately, the music from The Two Towers may have helped smooth things over (though the players raised their brows when they found treasures wrapped inside worg furballs)
Get The Two Towers soundtrack if: you want some good high fantasy music to play in the background for good chunk of your session.
Don’t get The Two Towers soundtrack if: Once again, music from The Lord of the Rings does not work well with grimdark campaigns–except for maybe, that setting Midnight, by Fantasy Flight Games, which is pretty much Middle Earth if Sauron had won.