Bob Rock was the new producer credited with Metallica’s 1991 album, commonly known as The Black Album.
Rock had already worked with major rock acts, and Metallica hired him after he criticized the sound and production of ...And Justice for All. His approach emphasized a stronger bass presence, more compact arrangements, and a polished studio sound without removing the band’s heaviness.
The album’s production credits also list James Hetfield and Lars Ulrich, but Rock is the principal producer named in the album’s production information. Randy Staub served as engineer, with Mike Tacci assisting him.
Recording was demanding. Sessions at One on One Recording Studios in Los Angeles lasted roughly eight months, and the band and Rock sometimes disagreed about how the songs should sound. The finished album nevertheless became a defining example of early-1990s heavy-metal production.