I *always* have thoughts about this.
I so totally know what you mean! And especially for Triumvirate (since I know you are/were on that one). I'm not kidding, when I was still planning to transcribe that episode I was already mentally transcribing the musical notes in certain parts because that episode uniquely features the music as if it's a guest star. (elevator scene, hello!)
I don't *usually* mention the music, but there are most definitely times when I have because it's a more obvious part of the storytelling. It's certainly up to each transcriber, but there are *those times* when a mention of the music is not only acceptable but
appropriate. Especially for recurring themes or when there is no dialogue. I most definitely don't feel that's it's too much to mention.
Mentioning it every time it happens would be excessive, but
never mentioning would be excessive too, IMO. It's part of what's happening. I'd say mention it whenever it's something you think a casual observer might consciously notice, and go with your gut.
Happy decision making!
EDIT (because IWSOD makes some good points):
ITA that transcripts can never fully replace watching the episode. However, mostly the people reading the transcripts are going to be *US.* As avid fans, we are likely to already be familiar with the episode, and the transcripts are not
replacing anything. They are
recalling moments that we probably already have seared into our brains (or want to have seared into our brains, if only we could remember...hence the transcript). Also, speaking as someone who was out of the fandom for a long time, descriptions can be crucial to jogging memory. I speak from experience when I say that if I'm reading a transcript and I have little or no knowledge of the episode, I'm going to want MORE explanation, not less. Frankly, even a bad or biased explanation gives more of an idea of what's going on than no explanation at all. It gives a reason to compare it to the episode later and find out for yourself, if and when you get the chance.
I know, we're all afraid of being too loquacious--and it's a healthy fear to have--but transcribing is a long-winded and laborious work. That's just the way it goes. By the time you get done with it, you have miles and miles of words. And that's even if all you did was transcribe the dialogue--which is NOT what Petra says she wants. IMO, I think the fear is a bad thing when you start to feel like, "Well, I've already written a whole lot...maybe I should start shaving off the facts...?"
One more thing I want to point out is that there have been countless times when
reading about plot exposition--like a joke, for instance--has, embarrassingly enough, made me GET the joke because I didn't quite catch it as the episode was whizzing by and my other senses were engaged. So that's another reason too why I would argue in favor of explanation vs. omission. You don't
always have to be watching an episode to appreciate something you can't see/hear.
We're fans. We've probably already seen it. Excessively.
And sorry for the answer-in-essay-form. Transcripts have been my bread and butter in a number of fandoms. It's made me develop some strong opinions about them over the years.
And under-explaining is OBVIOUSLY not my problem.