Producer Brendan O’Brien was fresh off wrapping work on Pearl Jam’s sophomore album Vs. when he met Chris Cornell for the first time in the summer of 1993. Cornell and his bandmates in Soundgarden were nearly finished recording what would become their smash album Superunknown, and, per a recommendation from Pearl Jam guitarist Stone Gossard, invited O’Brien up to Seattle to discuss mixing the project. As O’Brien recalls, “We went out to dinner to talk about what we were going to do, and five minutes in, it was like, ‘Are we actually going to talk about mixing? We’ll put the songs up and make it sound good. What’s next? What do you want to talk about now?’ We all just laughed, and then bullshitted for the next hour-and-a-half.” Released the following March, Superunknown became Soundgarden’s...