Elvis star Austin Butler reveals advice given to him by Leonardo DiCaprio

"Leo told me, 'Baz is going to constantly keep you off balance, and it's going to pull things out of you you never knew you had inside you,'" Butler told Entertainment Weekly.

"That's exactly the experience that I had.

"There were days where I just thought, 'Baz, why don't we just do what we prepared?'

"I realized that he would push me right to the edge of what I was capable of. You capture lightning in a bottle in a way — if you had just done the thing that you had prepared, it may have been more stale."

Luhrmann like a jazz musician

Butler continued by saying that Luhrmann works like a jazz musician in that sometimes he takes things in a different direction if it feels right.

"In order to play jazz, you have to know music theory," he explained.

"You have to know the scales on that guitar inside and out, but at the end of the day, you're improvising. You have all this knowledge and practice that is then going into this present moment and playing off whatever's in front of you.

"That's how Baz is because he works so hard at preparation. When it comes time to actually film, I'll have been preparing a scene for a year, and suddenly, the day of, the entire scene changes."