LA Times published an article today about actors who have played singers in recent months. This is the quote on Natalie and Vox Lux:

Months before shooting began, she also recorded a selection of tracks written by Sia and singer-songwriter and producer Scott Walker — it was the first time she’d ever been called on to sing so extensively for a role.

The experience left her with newfound respect for hit-makers and performers. “Pop stars are this incredible force of nature,” Portman said. “There’s a mystery there, an internal force that propels them. It’s a really hard life. You watch any of these documentaries, and it is so much work. I think what [makes them such fascinating figures on screen] is that special charisma that everyone is attracted to combined with this unbelievable work ethic and then the very human toll it takes.”