While obviously another apples and oranges situation, Akira Ifukube went in and out of scoring Godzilla films over the course of 41 years, continuously incorporating themes from earlier installments in new ways and all while adding to the franchise's musical lexicon with new thematic material that seemed to stem from Ifukube having, like Williams with Star Wars, an infinite number of things to say about his defining franchise. After scoring his last Godzilla film at 80, Ifukube concluded a musical relationship that had lasted more than half of his life and that comprised approximately 15 scored entries.
Again, to compare Williams to Ifukube is pointless. Apples and oranges and what have you. Some may scoff at even attempting to draw a parallel between the two. Regardless of personal opinion, Ifukube's relationship with Godzilla highlights a unique music career distinction shared with the likes of Williams and his relationship with Star Wars, a distinction that makes the Star Wars scores so largely tantalizing to me.
This is to say, you have a composer who defines their career with a single film and throughout the course of multiple decades (that see both the franchise and the composer grow and change in ways not realized during the inception of the first installment) that same composer repeatedly comes back and somewhat literally has to confront the writing style of an older incarnation of themselves that no longer exists. How the composer chooses to deal with that confrontation of a previous musical identity, either through embracing it and trying to write in a style reminiscent of those years of old or by adapting and updating that identity to conform to the new musical norm for the composer, is a dilemma both Williams and Ifukube had to deal with. One of the greatest benefits in being an observer to this unique relationship as a listener is being able to more directly than usual realize and appreciate the growth a composer has had. For example, Crumbs has said before, and I agree, that Rey's theme is representative of a piece Williams couldn't have realized even 15 years ago. Yet, at least to me, Rey's theme, while being a creation deeply entrenched in the writing sensibilities Williams is currently in possession of, fits perfectly within the Star Wars musical landscape. You get to be witness to great musical moments like the build to the Rebel Fanfare statement followed by the perfect segue into Rey's theme in The Battle of Crait, whereby you have a seamless bridging between the music of new Williams and the Williams of old. Those moments, those decisions the composer had to make in trying to consolidate different sensibilities, are so delicious to be able to observe.
Once again, as is usually the case when I decide to create a post on here consisting of more than two sentences, I have taken to rambling. I guess ultimately what I'm trying to say is that, while we can all find instances that are at least partially comparable to the journey Williams has taken to crafting and now having to conclude a three trilogy saga, such instances are incredibly limited. As others have put more eloquently than myself, we are witness to a very unique musical occurrence and it'll be a treat to see how Williams chooses to conclude such a journey in just a few short months.