The Fighter star has been cast as the tragic rock icon in Janis Joplin: Get It While You Can but she is concerned her singing will not match up to the Me and Bobby MCGee hitmaker's famous voice.
She has been desperately trying to develop rasping tones by shouting and screaming loudly, but still fears directors will have to bring in a professional singer to help perfect the sound.
Adams tells Britain's The Times, "I've been working on my rasp. Just by tearing up my voice. I'm going to try to do as much singing as I can. But I'm also realistic, and I might need some assistance."
Joplin died aged 27 in 1970 from a drug overdose.