The singer took a deep dive into Holiday's life and career before shooting on director Lee Daniels' "The United States vs. Billie Holiday" began, and admits she adopted a drastic weight loss regime and started drinking and smoking to get into the skin of the music legend.
"I basically abused my body for a long time...," she tells Variety. "I got the role at the very top of 2018 (and started) reading everything I could get my hands on, listening to every interview. Apparently, I exhausted the Internet of Billie Holiday photos. Apparently, the Internet will tell you that you've reached the end."
"I put my family through it; I put myself through it... I went from 163 pounds to 124 pounds. I would talk like her and I don't drink or smoke, but I started smoking cigarettes and drinking alcohol. Not that I recommend people do this; I just was desperate because this is my first role."
"I just asked God to give me all of the pain and trauma. I asked him to give me her pain and give me her trauma."
Day also changed the way she sang for the role, adding, "Every time I would sing a song I'd go, 'OK, Lee's going to hear this and he's going to fire me.' But I wouldn't have done it if they'd been, 'Do it in your voice.' That, for me, would have probably been a no."
"There's victory and there is pain in her voice, so to me it was just like, 'We've got to get it, we have to get it,' you know what I mean? It'll have to be my interpretation of it, but it has to be there."
"The United States vs. Billie Holiday" drops on Hulu on 26 February.