Renée Zellweger claims shooting 'Judy' was two years of "experiments".
The 50-year-old actress insists she didn't worry too much about achieving the distinctive look and sound of the late Judy Garland in the new biopic but she and the team behind the movie just kept trying new things until they figured out what worked.
Asked if she had worries about being like Judy, she said: "Oh no, I just didn't let myself think about it like that at all, or what might happen. Every day for two years, pretty much, we were doing experiments - we just kept trying things until here we are."
One thing that helped Renee get into character was her costumes, which she was "literally sewn" into but they forced her posture into that of the 'Over the Rainbow' singer.
She told talk show host Graham Norton: "Judy slouched a little and the dresses were made so that I couldn't have stood any other way.
"I was literally sewn into them.
"It was a great reminder during the day if you got lazy because you had no option but to stand like her. The sequins were very strict!"
The movie depicts the singer-and-actress' final few weeks before her death but Renee insisted that doesn't make for a "depressing" film.
She insisted: "It's not depressing and you can't help but empathise with her. She's not tragic at all because she didn't quit. She's heroic."
The 'Bridget Jones' Diary' star became a household name thanks to her role in 'Jerry McGuire' and she admitted she learned a lot from her co-star, Tom Cruise.
She said: "It changed my life overnight and Tom was the best teacher."
The full interview with Renee airs on 'The Graham Norton Show' on BBC One on Friday (04.10.19) night.