Eyebrows were raised when British actor Tom Hiddleston ('The Avengers,' 'Thor') was chosen to play Hank Williams in the upcoming biopic 'I Saw the Light.' But if there was any question about the actor's ability to conform to the country music star's image, they were quickly laid to rest when he performed at the Wheatland Music Festival in Michigan over the weekend -- for everyone but Hank Williams III.

Hiddleston sang Williams' big hit, 'I'm So Lonesome I Could Cry,' while tunesmith Rodney Crowell, who is serving as the film's music director, strummed along on the guitar. But while his performance might seem effortless, the actor says he's been working very hard to sing just like Williams.

"I've already started singing and playing every day," Hiddleston tells the Daily Mail. "Hank’s life has a tragic arc, but in simple truth, he was a genius: a star that burned twice as bright and lived half as long. It’s a huge role for me and a huge responsibility. I’m going to give it everything I’ve got."

While the 33-year-old is committed to portraying the singer accurately, Hank III says Hiddleston has "got no soul or moan in [his] voice" (quote via Saving Country Music). After casting was originally announced, Williams' grandson voiced his displeasure over the choice of actors and pushed for Matthew McConaughey to take on the role instead.

“To do a Hank Williams movie the way it should be done, you need certain aspects in the mix to make right,” he explained. “The main reason I said Matthew McConaughey would be a good person for this role is because of he has played many roles as a Southern man. And he is from the South. And that is something no amount of money or acting classes can put into a role.”

'I Saw the Light' is scheduled to begin filming in October in Louisiana. The film will cover all of Williams' life, from his early years up until his untimely death at the age of 29, which was blamed on his years of substance abuse.