Bob Rock was Metallica's new outside producer during the recording of The Black Album.
The band chose Rock after hearing his work on Mötley Crüe's Dr. Feelgood. Metallica wanted its best possible record and believed Rock could help achieve a more powerful, accessible sound. He became the first producer to work with the band on an entire Metallica studio album.
Rock changed the band's studio habits. Instead of constructing many parts separately, he encouraged the members to play more collaboratively and pushed for live-feeling performances. He also helped make Jason Newsted's bass more audible, a notable change from the controversial low-bass mix on ...And Justice for All.
The producer and band frequently argued during the sessions. Rock later described the experience as so stressful that he briefly vowed never to work with Metallica again. Nevertheless, he returned for the band's next studio albums, including Load, Reload, and St. Anger.