Which recording studio did Metallica primarily use for The Black Album's sessions?

Metallica primarily recorded The Black Album at One on One Recording Studios in Los Angeles.

The main sessions began there in October 1990 and continued through the album's demanding production period. One on One was a Los Angeles facility associated with large-scale rock recordings, making it suitable for the band's powerful sound and extensive overdubbing.

Metallica also worked at Little Mountain Sound in Vancouver for about a week. Final overdubs and mixing were completed at A&M Studios in Hollywood during June and July 1991, so the finished album was not created in one location alone.

The band recorded many takes while pursuing the right feel. Producer Bob Rock encouraged the members to play more collectively, while the drum performances were retained and other parts, including guitars, bass, and vocals, were overdubbed afterward.