So, Corbomite was the first produced, right? But it open with Kaplan's fanfare, doesn't it? (I'm making that assumption based on the fact that it is part of Label X's recording of The Enemy Within and it open The Doomsday Machine as well.) So how much later was that recorded? I'm trying to figure out the rhyme and reason of what was recorded when vs. what was used when. Whacky I tells ya.
A lot of episodes spent longer in post-production than others due to their visual-effects requirements. "Corbomite" had some pretty elaborate optical shots, requiring three new miniatures and a lot of composite space shots, so that must have delayed its completion. I'd assume that scoring was one of the last stages of post-production, coming after the effects were in. So by the time "Corbomite" was ready for scoring, there was already a fair-sized library of stock cues available to track it with.
I'm pretty sure the reason some of the scores are short is because only the original content is being included, not music lifted from other episodes.
Well, that goes without saying, doesn't it? Of course those cues are included with the episodes they were recorded for. No point in duplicating anything. Tallguy
's point is that it's surprising how little original music some of these "definitive" episodes had in them.