Hammett reveals in a new interview with AltPress that the band has been working with Greg Fidelman (Slayer, Black Sabbath, Slipknot, System Of A Down, Adele).

The guitarist says, "We're pretty much doing it with Greg Fidelman."
But he then adds, "He is in the mix. As far as what the final outcome will be, I don't know. We have not brought in any [other] producer and it looks extremely [unlikely] we'd bring one in this late into the project."

Hammett then explains how Fidelman's approach differs from other producers, "The title 'producer' itself is a bit ambiguous. It differs from person to person. You can call Rick Rubin a producer, but he's not the [same] type of producer as Bob Rock, who is there for every note. At the same time, Rick Rubin gets stuff done.

"Greg Fidelman is a different type of producer in that he's with the engineer always looking to try and move the project forward. And that's different from, say, Dr. Dre, who is the type of producer who is actually making backing tracks, producing music, writing music. In the hip-hop world, Dre is a producer. It's so ambiguous. If you go by the traditional term, we're doing it with Greg, pretty much."

As for Fidelman's credits, AltPress named a number of projects that he either produced, mixed of engineered including Metallica's last studio album "Death Magnetic," as well as material from Slayer, Black Sabbath, Slipknot, System Of A Down and Hammett added, "He did the first Adele record, bro! He's done all sorts of stuff. Greg is a real pleasure to work with. Even though he can be a bit of a taskmaster, he listens to you. He's super-flexible. He knows how to crack the whip without f***ing pissing people off."