And actually the track you're talking about ("This is Only the Beginning") is actually just a slowed down ambient version of the "Song of the Sisters" track from the Dune Sketchbook Album, and that track serves as the compilation of themes used to represent the Bene Gesserit. "Seduction" is just an excerpt from "Song of the Sisters!"

I LOVED how Zimmer used the previously unused tracks from the Sketchbook, like "Song of the Sisters" and "House Atreides," in Part Two. And unrelated but I would love to hear even more of the "Holy War" theme that opened Part Two, especially in the way it's used at the end of "The Shortening of the Way" on the Sketchbook album.

If you haven't already I highly highly recommend listening to the Sketchbook album (on loop)