I think the first and third track in FotR soundtrack stand out as representing a very different style than any other piece in the whole trilogy. And maybe it's as it should be considering those songs tell about ancient times when the Numenoreans came to Middle-Earth.
The 3rd piece opens with a soft and kind of eerie feeling. Strings back up the solo wind instrument beatifully. After that (1:00) it's a musical mess of different themes. Of course it supports the film perfectly but as a separate piece it's rather anxious and oppressive. I don't really like this track though it has some very nice elements in it because it makes me feel uneasy.
Like Encaitare already pointed out, there would seem to be a little hint to Shelob's theme i.e. the creepy glissando (sliding).
The brass instruments reflect the Gondorian culture though we don't hear the Gondor theme yet. On the other hand Mordor and Isengard use the brass as well so perhaps those wind instruments we hear on the 3rd track refer to Gondor being somewhat under the influence of Mordor.
Btw, I recommend all of you who are interested in LotR soundtracks to visit
http://www.elvish.org/gwaith/movie_soundtrack.htm . There you find the lyrics and translations for almost every piece in the trilogy. And if you can get a copy of
Music from the Movies (issue 42...I think it sold out) LotR special with 90 pages or so filled with interviews and pics, read it! It provides a nice survey of the film score.