From Alex Ross’s terrific interview with Jonny Greenwood:
There are scenes in “Spencer” that require your music to be already in place, like the Christmas Eve dinner where Diana has a breakdown while a string quartet is playing.
It’s just as described in the script: it starts as conventional dinner music and unravels, as Diana does, over the course of the scene. But, again, there’s a sign of how I’ve been indulged. Pablo said it needs to be a few minutes long. So I wrote it, and he cut the scene to that. Which was lovely, because it meant that all I had to do was write this piece of music and have players play it in a room without thinking about a time code and all of that stuff. It breathes. They are playing to each other rather than playing to a film.