One thing that’s interesting to me in JW Rinzler’s Howard Kazanjian biography is that allegedly one reason David Lynch turned down doing ROTJ was that he didn’t want to make a film that would be scored with John Williams’ music. I know Lynch generally prefers unsettling audio tracks rather than orchestral music pieces in his own work, but it’s still frankly startling (and certainly ballsy) for a a director to say they wouldn’t want a John Williams score if they directed a Star Wars movie.
I wonder how he felt about Toto’s work on DUNE. Was that something Dino De Laurentiis insisted on, perhaps?
From what I’ve understood Lynch simply didn’t like the idea of making a film according to someone else’s ideas, i.e. being restricted by Lucas’ story ideas. The music might have been a part of this concern, but I think Lynch simply didn’t care for SW.
Lynch talks about his meeting with Lucas in this 3 min. video;
https://www.youtube.com/watch?v=EJQ4vCu-S0U&t
As for the Toto music in Dune, I’ve been wondering about this as well, but I suspect the Brian Eno music was more in line with Lynch’s wishes and that Toto was De Laurentiis’ idea, though I still get the impression that there was a direct collaboration none-the-less. It’s hard to tel with Dune because it’s not like Lynch was kicked off the project but rather that he was contractually strong-armed into making multiple changes to the film against his original vision. So ironically he ended up in a similar position to hat he’d have to endure if he’d said yes to direct ROTJ.