Yup, the maelstrom is another case, we get some of it, thankfully, but not the whole. The 2 best sequences in the entire trilogy and we don't have the full music.
Unfortunately, most composers have control over the scores, which is why often tracks will actually mix cues from varying scenes of the film, they like to make the CD almost like a portfolio of their work on the film and arrange it how they want it, rather than give every note from the film or keep the cues in context of film order. I'm not familiar with the Lord of the Rings complete scores and how true those are to the name, but of ones I've encountered, only The Phantom Menace Ultimate Edition actually captures every not, in exact order, from start to finish from the movie, and I love it for that, too bad it's not my favorite of the Star Wars scores. I'd love to have complete, start to finish scores for all 3 Pirates films, Nolan's Batman movies, and the Star Wars saga, but sadly, it doesn't seem like it'll ever happen.