American film A STAR IS BORN, which was screened at the Toronto International Film Festival (TIFF) 2018 on Sunday, marked American singer-songwriter Lady Gaga's debut as a leading actress, media reports said.
"I don't know that I've ever had a closer artistic friendship with someone as I do with Bradley," multiple Grammy-winner Gaga declared in Toronto on Sunday, during a TIFF press conference for the film.
"This entire experience was life-changing. I have never had an artistic experience like this before."
Bradley Cooper, a music fan and Metallica devotee spent years developing the film, learned guitar and piano for A STAR IS BORN.
Cooper tweeted, "It's one thing to sing in the shower. It's another thing to sing in front of 20,000 people."
Gaga - referred to by her real name Stefani (Germanotta) by her co-stars- also created "harmony" with all of the other songwriters who wrote for the movie, including Jason Isbell, Mark Ronson and Lukas Nelson.
She (Gaga) kept the bar high, music-wise, Cooper said. "It all had to be up to her level... Stefani was very adamant about it," he explained.