For Bull, going out front by herself - she asked her sister if she minded - was just one of the challenges of taking on James, who delivered classic songs like the show's titular one as well as I Just Want to Make Love to You, A Sunday Kind of Love, I'd Rather Go Blind, and Something's Got a Hold of Me.
"It's a completely different thing being up front and having to carry a show. It is tough. I enjoy backing singing. I love that a lot ... but coming up front to sing lead it is a completely different kettle of fish. You do have to entertain and not just stand there. That's tough."
Bull and band have taken the production throughout Australia since the beginning of last year. The singer says Aucklanders will see a slicker show than before. Though Bull isn't doing a full James look - there's no trademark blonde bouffant.
"I did think about that. Will I dye my hair blonde? Will I do a blonde wig? But I just went nah ... and she liked a bit of bling and glitz. So I wear a bit of jewellery but try to be as comfortable as I can because it is a very tough show to perform." "
James' life story doesn't lack for drama. Born to a 14-year-old mother, there was an abusive childhood, drug addiction, time in a psychiatric hospital and rehab, all disrupting a career which won her three Grammys in her later years. It's a big life to interpret - and a lot of hurt to get into the songs.
"Life experience helps a lot - I've made a few mistakes in my life too. I didn't have anywhere as hard a life as Etta did. But you just try and draw from that."
Live music preview
What: At Last: The Etta James Story
Who: Vika Bull
Where and when: ASB Theatre, Aotea Centre, Auckland tomorrow