I think we just got lucky when it came around time to do the trailer. We got really lucky that [my main theme] just, it lied in perfectly against that song, you know? That was one of those things where they sent it to me, and they were like, ‘Should we fill it in more?’ And I’m just like, ‘I don’t know. It sounds pretty great the way it is and the way that it’s just sort of layered in.’ And we gave them a few things to add into it, but not much at all. I feel like they did a really good job with that trailer. It was a great way of saying, ‘Here’s your next Batman.’
Giacchino also talked about the film’s main musical theme (which we first heard in the “Camera Test” released by Matt Reeves earlier this year)…
I just had an idea one day and I was like, ‘Oh, this, you know, in knowing the character that Matt is bringing to the screen, I just thought this, to me, feels like… if I were Batman, if I were Matt Reeves as Batman, what would be going through my head as I stood up on top of some building and just looked at the city?’ And I thought, ‘Yeah, this is what would get me going through my head.’ And so I wrote that, sent it to Matt and he really loved it. Then we had a chance to record a bunch of it when I was in London at one point, we did that, for no other reason than to maybe use it for trailers. I know Matt most importantly just wanted it to be able to edit with it. I wrote like 40 minutes or so of music, none of which to anything pictorially. It was just sort of like, ‘Well, here’s what I’m thinking, you know?’ And so who knows how much will last, and how much we’ll look at later and go ‘It doesn’t fit as well as we thought.’ But that particular, very simple main theme, you know, that’ll be there.
Good stuff! Click on the links provided for the full interview. – Bill “Jett” Ramey