When Rage Against the Machine guitarist Tom Morello released The Atlas Underground in 2018, it was his solo debut, but only nominally so. He had already released albums under the name The Nightwatchman for over a decade, and the project saw him sharing the spotlight with huge names from hip-hop like Big Boi and VIC MENSA as well as dance and electronic music kingpins like Bassnectar and Steve Aoki. Coming barely a month after the similarly packed The Atlas Underground Fire, The Atlas Underground Flood continues the name-checking and genre-mashing on somewhat more familiar rock terrain, with contemporaries such as Jim James, IDLES, Manchester Orchestra, Metallica’s Kirk Hammett, and Rush’s Alex Lifeson along for the ride.