What does this mean? Well, just as you wouldn't give cellphones to characters who're supposed to be in a pre-industrial age world, you might want to consider avoiding a modern orchestra when writing music for a pre-modern orchestra world.
This all has a specific point, and that point is why I just created a "project crazypants" tag. I should probably also create a "Lord of the Rings" tag, except I'm pretty sure I wouldn't ever use it separately from the project crazypants one, so why bother? I'm certainly not going to be writing fanfic for it, so. (There's nothing I want to fix! For the book, at least.)
My point (finally getting to it) is that all the music in the LotR movies is completely misused, and here's how I'd do it if they'd asked me: lose the orchestra. Lose the highly repetitive themes that become kind of annoying after the first couple of viewings. And replace it with something much more spare. What instruments would actually be available in Middle Earth at the time? Try to stick to those, and keep the size of the ensemble to chamber orchestra, at most. Also, if you're going to have songs in the movie, use some of the ones in the book. (There's an awful lot of them, and I should know: I typed them all up one week when I first got this bee in my bonnet. It took a while.)
Actually, the real point of this is that I wanted an excuse to share this video, which shows the range that can be produced by a few period instruments. Also, it's nice background music.