Is the voice speaking in a language and idiom the viewers know well? Is it on or off camera? Is anything else happening?
Is it a professional voice, like that of an actor or a hired voice-over artist?
Is the music interesting (full of surprises) or is it written to be in the background? (Do you know why so little Beethoven is used in film? Because it takes all the available attention away from whatever else is going on. You could say the same about Frank Zappa.)
How much is a proper pich of salt?

I'm putting these provocative questions to you because I think there is no recipe for what you're cooking. You have to just put your spoon in and taste it. Perhaps try it on a couple of people who doesn't know the words by heart (like you probably do by now).

I'm in the middle of a problem not unlike yours: I'm editing video from the ceremony when my father in law received the King's medal of honour (Indeed, for having put in 50 years as a non-paid sunday school teacher).
The material is neccessarily full of lengthy speaches. Besides cutting them down to the bone I'm trying to gate out the camera noise (didn't know the Sony PD 150 was so noisy) and in some places I add background music to camouflage the resulting holes. Whenever someone reads a poem I subtitle it. And at the emotional climax I pull the music way down and the voice way up in a manner that looks rather drastic on paper. But on paper is not where it will be.

Someone has said of film music: if you can't remember it, it's good. That may not be entirely true, but perhaps you could say that about background music? Anyway it's not supposed to draw attention to itself. Keep the background back.

Tor