Cluster chord in the Hobbit Soundtrack

In the Hobbit : An Unexpected journey - Moon Runes there is a cool cluster chord in the French Horns at around :47 to :57

Howard shore uses these cluster chords a lot in his Lord of the Rings, to build tension.  Here's some more examples, from the fourth track, Axe or Sword

At 2:37 - 2:56 : Interesting building dissonance


3:37 - 3:45 : There it is again, in the horns instead of the strings


4:04 - 4:18 : Again, but strings and horns