Flash was born as Joseph Saddler in Barbados in 1958, before immigrating to the United States and settling in the Bronx with his family as a child. In his youth, Saddler enjoyed tinkering with electronics, and his mother sent him to vocational school with the hope he would find steady work as a television repairman. Instead, the young man combined his aptitude for technology with another early love—his father's massive record collection—and reinvented himself as Grandmaster Flash, stepping into the public eye by expanding on the innovations of his predecessors in the thriving New York DJ scene of the mid-1970s. Fellow Bronx turntablists DJ Kool Herc and Grand Wizzard Theodore had laid the foundations of hip-hop DJing by introducing the looping of break beats (i.e. isolating the short drum solos on rhythm and blues tracks) and scratching, respectively. To this vocabulary Flash added his own innovations: "backspinning," in which the DJ plays the same record on both turntables, isolating the hook or the beat on both and switching back and forth to generate an endless sonic loop; and "punching," in which the DJ hits isolated phrases from a record as a rhythmic accent over the existing loop. On the strength of these developments, Flash amassed his own loyal following among New York b-boys, and in the style of his DJ predecessors, assembled a posse of MCs to complement his turntable wizardry with rap. Thus, the Furious Five was born, featuring, on the mic, Grandmaster Melle Mel, Cowboy, Kidd Creole, Mr. Ness, and Raheim.

In 1979, black music impresario Bobby Robinson signed the group to his Enjoy Records label, for which the Furious Five recorded their first single, "Superrappin'." An innocuous party jam, this initial studio venture is largely a bouncy advertisement for Flash's greatness, evoking the energy of the group's early performances with lyrics that boast endlessly of the DJ's brilliance. A year later, the Furious Five migrated to Sugarhill Records, the label that made rap nationally marketable with the massive success of the Sugarhill Gang single "Rapper's Delight." For the new label, Flash continued to showcase his turntable mastery in self-aggrandizing efforts like a notable remix of The Incredible Bongo Band's "Apache," and an epic 12-inch single collage of pop and dance music he called "The Adventures of Grandmaster Flash on the Wheels of Steel." (One of the records Flash integrated into this mix was Blondie's "Rapture," which famously namechecks the DJ in Debbie Harry's rap verse.) In 1982, though, Flash and the Furious Five released their most influential and enduring single, "The Message." Centered not on Flash's technical virtuosity, but instead on his MCs' gritty lyrics about contemporary urban life, the record was notable for two chief reasons. One, it effectively redirected Hip-Hop's lyrical content away from party jams and toward social commentary - setting the stage for later MCs as far-ranging as Public Enemy's Chuck D., N.W.A.'s Ice Cube, Tupac Shakur, and Eminem. Secondly, the song shifted the focus of the Furious Five away from the DJ and toward the MCs. This latter change governed hip-hop's development throughout the 1980s and ever after. While the DJ as a figure was the genre's early hero, since the 1980s, the voice on the microphone has reigned supreme.

Flash was a DJ, not a rapper. Back in the day, the DJ was the star and the rappers were there to add some flavor and hype him. As the rappers (or MCs) became the stars in the '80s, many people assumed Flash was on vocals.