The E.T. Soundtrack holds a very special place in my heart, so I occasionally call back in appreciation of Williams’ influence on me as a composer. Those transitions are inspired by the E.T. soundtrack, a quite intentional nod. Windfall is another piece - you can find it here on YouTube - where I also call back to E.T. at the climax near the end.
In fact, when I rehearsed this piece with my band, I constantly referred to these as the E.T. / Williams measures. True story.
So, about that b9 interval in beat 4 of 156...
Maybe the Gb bass note along with the Gb in woodwinds, mallets, etc is setting up a sort of resolution that G natural thwarts? If we look at these two measures, the linear material is building into the final conclusion of the work, so when the last beat of this line extends us suddenly to a b9, I think it fulfills the point of these two bars building to 157.
I distinctly remember spending more time on these measures than other measures of the piece thinking, “Why does this seem to sound more effective when the line goes to G instead of Gb?” And I remember reading somewhere that the b9 interval is actually one of the most dissonant intervals in large orchestrated works (this is probably more debatable in theory, so don’t take my word as law on that), so b9 has its uses if you’re aware of its dissonant impact. I may have ultimately, and accidentally(?), discovered a moment where it actually works.
Thanks for listening! I hope some of this is helpful in explaining things in a way that’s beneficial to you. If not, I’m happy to break it down more in discussion. Cheers!