The 36-year-old actress is set to play the Texan songstress – who died of a drugs overdose in 1970, at the age of 27 – in the biopic Janis Joplin: Get It While You Can, to be released in 2012.
'It sounds so weird to say, but Janis was a big personality with a lot of spirit,' The Fighter star says in an interview with the Los Angeles Times supplement, The Envelope.
'I put it in her hands. You have to surrender at some point.'
Adams has launched a successful career playing sunnier roles in movies such as Enchanted, Julie & Julia, and Doubt, in which she plays a nun.
But she denies that playing Joplin is a deliberate tactic on her part to play grittier roles.
She says: 'I understand how people find the commonalities in the characters I've played.
'But I never thought I was stuck in a rut, so I didn't feel like there was anything to get out of.'