I'm starting to think of Ghost in the Shell once more. I should mention that I mean the entire corpus--both series and films. What got me started was the music used in both realizations.
If we progress linearly in terms of the story's timeline, we start with Yoko Kanno's work in "Stand Alone Complex", then to "2nd Gig". After these are the two films, one simply self-titled and the other being Innocence (also known as Ghost in the Shell 2: Innocence). The two films were scored by Kenji Kawai.
When considering Kanno's music in the two series, I get the feeling that the music is deliberately crafted as pop music residing in layers of technology. Or, if you like, it's catchy music in the spirit of The Beatles' "Sgt. Pepper". (I should mention that she does have her eclectic moments, breaking with the usual song structure.) The two films, on the other hand, tend to be different in term of music. They do have some hook-driven songs, e.g. "Follow Me", but Kenji's music is mostly on a different track. It ranges from bombastic percussion to minimalistic soundscapes.
I mention this because the music itself evolves with the entire corpus of Gits. Consider this: We have reached a certain stage where we're surrounded by technology. It's almost everywhere, and we've become fairly acquainted with it. However, there are still some surprises here and there; stuff we can't figure out or completely control (e.g. hacking cyber-eyes, the nature of the "ghost"). This is the situation in both "Stand Alone Complex" and "2nd Gig". It's still pretty much humans adapting to technology. Hence, we see the neat stuff the we can do with it (something the first series tends to do a bit too much, at times). Kanno's music for both series mirrors this predicament or situation. And, she does this very well. If she had done something else, it wouldn't really match the context of those series, the initial struggles and epiphanies they encounter.
Now this: We've become even more adept with technology. There are still hard "problems", but they've taken on a different light--the "ghost" isn't exactly a problem to be solved; it's something we have to engage with, since it's essentially us. (Think of it this way: We don't solve music; we already know it. But have you ever asked what is it that you "know" about the music in question? Perhaps that's the wrong word, since music is something we "feel". Still, you know what that feeling was communicating when it was doing it.) What that "us" means, of course, takes us quite farther than the series does. With that, Kenji's scores aren't really progressions of Kanno's. In fact, Kenji's almost sound like tradition standing in the face of something never encountered before. Like something that's come into being, and its presence greatly affects you.
Kanno's score reflects us acquainting ourselves with our newly created environment and with all the newly created entities that follows it. It's still "us and the environment", as it were. Kenji's score shows us blurring the distinction between between humanity and this self-created environment, yet it has to do this via tradition. It's now more or less: Something has come into being, and it has fundamentally changed us; therefore, the old boundaries no longer apply. Let's see what we are now.
I'll admit that this isn't very clear, since I've yet to fully clarify it to myself. But I can't shake the feeling that most of what I've written here gets closer to what the entire corpus of Gits is doing, compared to what my earlier thoughts had led me to think--viz. Humanity immersed in a world of technology, alone.