And the sex scenes are perhaps the one part of the whole Voice Acting thing that gives me trepidation to be honest. It's so easy for the moaning, groaning, sucking and slurping to come out sounding very corny and absurd. The actual dialogue I think is the easy part because I know how it sounds in my head when I'm writing it. But it would be odd to have all this vocal action that then go silent during a sex scene. Alternatively, it would be just as bad to have a bunch of superb dialogue that is suddenly ruined by poorly done sex sounds. Such a dilemma. Thankfully it's not something we have to think to hard about yet.1. Music - I think this can really set a scene whether it be sexual, romantic, or atmosphere. Like some people have said it should start low before it comes in so as not to jar the player. like in movies and tv music can really set the mood and turn an okay scene into a fantastic scene. It's all about context. Renpy already gives an option to turn off music so you won't have to worry about that feature.
2. Sound - As with music this can set scenes or moods if done right. It's not required but it can help some people get immersed into the world. Same thing don't make the sound effect super loud and you should be fine. I'll admit the only sound that matters to me in an adult novel is the moaning of pleasure from the female characters (Though this can be put under the voice section as well).
3. Voice - This can make or break a game experience depending on the voice itself. If the voice is good i'm all for it. If it's bad or cheesy, it depends on what story your telling. Like if your making a bad porn or something like that. I wasn't a fan of the Daughter for Dessert voice acting cause it's only in there for a short time so it is a little jarring to stop hearing it all of a sudden.
As @UncleVT said the voice acting in Sylvia is quite superb whether it be the english or french actress.
I'm all for an immersive experience. So these things being added can only be a bonus. I will still play the game if they are not because of the characters and the setting.
Keep up the good fight.
Excelsior
But it's there, in the back of my mind.