[1] He has worked with many groups and artists during his career, such as AC/DC, Pearl Jam, Stone Temple Pilots, Soundgarden, Red Hot Chili Peppers, Bob Dylan, Rage Against the Machine, and Bruce Springsteen.
[2][3] O'Brien was also credited on a plethora of nu metal albums with such artists as Korn, Limp Bizkit, Incubus, and Papa Roach Raised in Atlanta, O'Brien's career blossomed as a young guitarist with a local band by the name of Pranks, signed by what was then Century Artists Management.
The management company had what many considered the best of Atlanta and the surrounding region in those days, including the likes of Mother's Finest, Ezra Pound and a dozen other "super-regional" acts.
His studio career was propelled by the success of the first Black Crowes album, Shake Your Money Maker, which he engineered and for which he also performed guitar, bass, and "a potpourri of instruments".
He produced the Italian bluesman artist Zucchero Fornaciari's 2016 album Black Cat and received production credits for track three of the 2017 EP Cold Dark Place by the progressive metal band Mastodon.