And in "Requiem for Methuselah," did it really make sense for science geek Spock to be such a liberal-arts expert all of a sudden that he could recognize Brahms's handwriting and Leonardo's brushstrokes on sight?
I see what you mean, but it would be even more
unlikely for Kirk or McCoy (or, really, any Enterprise crew member or the ship's computer) to recognize Brahms' handwritten music notation as his and no one else's
. Assume for a moment that there are a few thousand musicologists in the world today who would recognize a previously unknown manuscript as written by Brahms - probably the actual number is much less than that - and then extrapolate forward a few hundred years; hardly anyone alive then would have the necessary expertise to be certain
of such a thing, even if they had hours or days on Flint's planet to study it. But this is Spock, with the endlessly capacious mind, we're talking about.
The whole issue could have been finessed if Spock had said that by musical analysis alone - made possible by virtue of his memory of Brahms' whole corpus of work - he could identify the unknown waltz as the work of Brahms. But the visual element (our view of the manuscript itself) would have been lost. Perhaps Bixby even wrote it that way in the first place, with a verbal explanation only, and it was found to be ineffective as TV.
(I have always had great admiration for the waltz itself, by Ivan Ditmars - and I cringe at the thought that so many viewers of the episode over the years have only heard the syndication-cut, grossly abbreviated version without the contrasting central section. What a wonderful thing that the piece was commissioned for the show.)