Good direction is often based on the ability to communicate.
You can sing if you have a great voice, but to connect that instrument to the text and connect it to the subtext, what lies underneath and the emotion, is indeed a rare talent.
We have no filter for music, but we feel it when what's being spoken and sung is telling a story and evidencing a character.
What works in one medium does not necessarily always work in the other.
The challenge in any musical is unifying all the moving parts of it, in particular a movie musical because now you're adding the camera and you're adding the idea of adaptation. So the challenge is to stay as true as you can to the material that you love and yet not be afraid to step outside of it and introduce elements into it that make it exist in a satisfying, exciting way cinematically.
I think any musical has so many moving parts and the challenge is unifying all the moving parts in particular because you have the camera and now it's all about adaptation and what works in one medium doesn't necessarily work in another so the challenge is to stay as true as you can to the material and yet not be afraid to step out of it and add elements to make it satisfying cinematically.
