There's a scene in the movie where the climax is almost being set up, and you get a hint of the twist the first time, and to say the least its quite heartbreaking. I needed a track that gave off pure unadulterated emotion. Something that would portray that terrible feeling you get when you're almost choking from the inside and you don't really know what to do.
Now, I didn't have an awful lot of tools at the moment, so I tried modulating sounds to arrive at that place sonically. I made strings go through flangers and ring phasers, and the outcome was, to understate it 'amazing'. A large part of the movie had things going on in secret, and there's this subtle underlying percussion that runs throughout the score, which kind of mirrors that thread of the story.
In the meanwhile, I finished up the pre-climax and moved into the domain of the actual climax. And you know how climaxes are. Everything needs to burn and die. You have to do the equivalent of killing your audience sonically and emotionally. Make it feel like nothing is ever going to be the same again. Chaos and anarchy is the name of the game.
I spent a lot of time thinking what the darker and angrier emotions of mankind would sound like. I ended up using a groovebox-like VST that gave me some interesting rhythm percussion. I fiddled around with it, changing and modulating elements, shifting their placement and making things a little more primal. It still sounded a little too refined. I basically destroyed it.
I made the entire groove go through so much distortion you probably couldn't tell it from a washing machine, and I parallel-processed with the clean signal, and faded the clean signal out as things got messier and darker. It was a good idea. And then there was this point of explosion where basically, you could feel everything burning inside, as well as outside. Even though it was the messiest part of the score, it was the probably the most brutal part of the movie, and you really want the audience to feel that.
..Aaand that's the story of how I almost destroyed the climax of a movie.