This is a short little scene, but it's absolutely the first one that popped into my head when I saw today's prompt. Anyone who has ever talked Star Trek music with me knows I'm a big big fan of James Horner's scores, particularly to STAR TREK III. And of all the themes he wrote, his theme for Spock is probably my favorite. Wonderfully understated and somehow both mystical and logical at the same time, it absolutely is a perfect fit for Leonard Nimoy's portrayal of the iconic character.
Following the rescue of Saavik and Spock's body from the decaying Genesis Planet, we are given a beautifully touching scene with Dr. McCoy. Having carried Spock's katra for the entire film, McCoy is now imploring the unconscious Spock for help in understanding what has been asked of him. He then confesses something that he could only do under present circumstances: being alone with Spock when he's not able to respond.
It's an extremely touching moment and one that is wonderfully underplayed by DeForest Kelley[mfn]It's also an absolutely perfect line written by Harve Bennett in what I think is the most underrated Trek film script[/mfn]. And in the background is Horner's Spock theme. I will also confess that this scene is only about 50 seconds of a much longer cue that serves as a lush underscore to seeing the captured Klingon Bird of Prey approach and land on Vulcan. Some people like to suggest that Horner merely repeated his score to STAR TREK II in this one, and while there are certainly repeated phrases (even in this cue), Horner's quasi-religious Vulcan music particularly at the end certainly stand it apart from the more bombastic action of the previous film.