Like D.C. punk and Detroit techno, Houston hip-hop has influenced musicians across decades, casting a net far broader than a single cluster of urban area codes. Maybe when somebody says “Houston rap” the only things you think of are purple drank, candy-colored low-riders (“slabs”), and the words “chopped and screwed,” but the hip-hop scene in Texas’s largest city has been a distinctive presence on the national stage since at least the early 90s. And since the mid-aughts it’s been all over the charts thanks to the likes of Paul Wall, Scarface from the Geto Boys, Chamillionaire, Devin the Dude, and UGK. It’s reached across oceans too: this summer UK rapper Dizzee Rascal released a song called “H-Town” that features Bun B of UGK and fellow Houston veteran Trae the Truth.

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Most influential of all—and most tightly linked to the Houston sound in the minds of fans—is the late DJ Screw. Beginning in the early 90s, he perfected the dragging, slowed-down chopped-and-screwed sound on literally hundreds of informal releases, and the style’s viscous, underwater feel has become synonymous with purple drank—aka “lean,” which is usually a mixture of Sprite and prescription cough syrup containing promethazine and codeine. Since Screw’s death in 2000, a huge chopped-and-screwed remix culture has emerged, cranking out syrupy versions of popular studio albums and mixtapes (I recently found one of Chance the Rapper’s Acid Rap). Seattle MCs such as Nacho Picasso and Key Nyata use a subterranean Screw-inspired sound, as do Miami rapper SpaceGhostPurrp and his Raider Klan crew. The chopped-and-screwed aesthetic has seeped into nonrap genres (vaporwave, witch house) and popped up in Chicago footwork music—on a couple tracks from his new Double Cup, footwork mastermind DJ Rashad seems to be reimagining the ordinarily frenetic dance style with DJ Screw in mind, right down to a vocal hook that refers to his favorite purple concoction. Screw’s influence can be felt even at the very top of the Billboard charts: Drake’s “Own It,” from the recent Nothing Was the Same, begins with spacey ambience and a slowed-down Wu-Tang sample.

Walker interviewed rappers and DJs, of course, but also radio personalities, pimps, ministers, label honchos, strippers, and others; Houston Rap is nearly 300 pages long, and for a photo book it’s heavy on the text, with no pictures at all on some spreads. The fact that so many people were willing to talk—and that some of them were willing to be candid about their own criminal misdeeds, or to carry on unapologetically about whacked-out conspiracy theories—suggests that Walker and Beste knew how to earn their subjects’ trust.

Houston Rap also includes a respectful photo of DJ Screw’s father, Robert Davis Sr. (aka Papa Screw), sitting in front of a huge airbrush-style painting of his son. Screw looks almost like an angel in heaven, his bright white shirt fading into the clouds around him. He died years before Beste began working on this book, but his presence in it is huge. Everyone who talks about Screw (and lots of people do) seems to love him—though his friends saw him as larger than life, he never acted too big for them. They reminisce about how Screw copied and sold cassettes by hand, how he’d get in a freestyling rapper’s face to see if he was genuine, and how his family was evicted four times because of all the noise he’d make hosting a steady stream of collaborators and buddies. The stories and photos aren’t always rosy or flattering, but they pull off what Houston Rap as a whole is trying to do: display dimensions of these artists and their community that can be hard to see in the shadow of their legends.