“Avengers” star Tom Hiddleston has “got no soul” in his voice when he sang like country legend Hank Williams, according to the U.S. singer’s grandson Shelton Hank Williams III said.

The 33-year-old English actor is set to play Williams in the biopic “I Saw the Light.” And to prove that he looks and sounds like the American music icon, he surprised revellers at the Wheatland Music Festival in Michigan with a performance on Saturday.

Hiddleston sang “Move It On Over,” Williams’ first major country hit in 1947, to the appreciative crowd. He returned on stage on Sunday to sing “I’m So Lonesome I Could Cry” with Rodney Crowell on Sunday.

His impromptu performances were generally well received, with commenters noting that he really does sound like the late legend.

Of course, there are also critics who don’t think that Hiddleston came close to Williams, doubting that actor would do an outstanding job playing the Grammy winner. One of his critics is the singer’s grandson Williams III, or simply Hank 3.

“Here is how you do it TOM, You got no Moan or Soul in your voice,” Hank 3 wrote on his Facebook page, including a YouTube video of himself singing “Move It On Over.”

The 41-year-old musician thought that an Englishman like Hiddleston isn’t fit to play his American grandfather.

“To do a Hank Williams movie the way it should be done you need certain aspects in the mix to make it right,” Hank 3 told Fox411. “It goes way beyond having [an] American to play the role of Hiram Hank Williams, Sr. for it to be somewhat natural, [it] needs to be [an]American from the South who has eat, lived and breathed these kinds of roles before to make more respectable movie on Hank Sr.”

Hank 3 already has someone else in mind who could be a better actor to play his grandfather.

“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,” he said of the Texas-born Academy Award winner.

“The other reason I thought Matthew would be a good fit for the role is because he has a natural arrogance, aka fire, that is needed for ths role. Hank Sr. was very, very sure of himself and basically very cocky. And Matthew always brings that fire to the table in every role he [plays].”

“I Saw the Light” is based on Colin Escott’s biography of Williams, which will see the star’s rise to fame. Marc Abraham will be directing from his screenplay.

Hank Williams’ “Move It On Over”

Tom Hiddleston’s version