Yes! That is a nice little metaphor. Writing is a performance: you have time to sit down and think about things. And it's also artificial and constructed, because when you speak, you just say whatever pops into your head, but writing works towards something, and tries to establish something. You have to shape it to express exactly what you're trying to communicate, it can't be just any old thing. When you talk, if you say something wrong, you can quickly babble on and correct it, say what you meant - you don't have that kind of space in print because your reader will go cross-eyed and run off.

Fanfic - is it like different people performing the same song? Each brings their own vocal style, their own interpretation to the work - enhances some aspects and diminishes other.

That's what's always so exciting about a regular person starting to sing and turning out to have this incredible voice.

Yes!