Hot 97 was Jay Z’s home for the six straight summers he ran rap. He was featured in the station’s ad campaigns and on-air promos, and performed at Hot 97 sponsored concerts—The Player’s Ball, Hot Night Jamaica, and, most notably, three successive Summer Jams, from 1999-2001, culminating with a legendary set that featured the debut of his Nas dis record “Takeover” and a Michael Jackson cameo.

Naturally guarded, Jay even welcomed a Hot 97 DJ into his inner circle: “As his career started to take off and I’d have him on the show regularly, we clicked as friends,” Angie Martinez wrote. He also regularly played his new albums for her upon completion. Their friendship made for good radio; Jay was at ease opposite Martinez, often betraying his inclination towards reticence. “Angie had, like, the Bat-phone to Jay,” says Hot 97’s DJ Enuff. “I don’t know if they were trying to be a team, but it was definitely a team thing.”

Jay’s bond with Funkmaster Flex was more complicated, a business relationship built on influence and favor. Flex supported Jay, of course. Jay, for his part, contributed to Flex’s albums and made appearances at the Tunnel and on Flex’s show. It was and was not a quid pro quo. “Jay and Flex used each other as tools,” says former Hot 97 DJ Cipha Sounds. “They never clicked. They weren’t friends. They just knew each other’s power.”

Flex’s nightly show was also where Jay turned when he wanted to introduce his new artists. In the early days, Roc-A-Fella had a scant roster: mixtape legend DJ Clue; a ferocious rapper from South Philadelphia named Beanie Sigel; Jay Z’s longtime protégé Memphis Bleek; and Amil, who was dropped from the label shortly after releasing her debut album in September 2000. With the label’s next wave of artists on deck—a handful of Philly MCs in Sigel’s mold—Jay needed a platform. On the morning of January 12, 2001, he called Funkmaster Flex.

Following a conversation between Flex, Jay Z, and then-Def Jam VP Mike Kyser, it was settled: Jay would appear on Flex’s show later that evening, new acts in tow. And though he wouldn’t rap, he instructed Flex to “get the beats ready.” Flex then went for a drive. A car enthusiast, the Bronx-born DJ selected his instrumentals based on which knocked in his automobile. He also braced for the evening; DJing live for artists is different from mixing on the radio. “I’ve DJ’d for artists in clubs, and, um, I’m not very good at it,” Flex admits.

The Roc’s untested squad of battle rappers—Freeway, Oschino, Sparks, and Young Chris—also prepared for a potentially career altering event. Freestyles during Flex’s nightly primetime shift reached audiences beyond Hot 97’s broadcast range. DJs often packaged the rhymes onto mixtapes and compilations, while newfound peer-to-peer file-sharing services such as Napster spread the music online. The freestyles also lived on at Hot 97—a peerless self-aggrandizer, Flex often replayed highlights from his own show.

“I was ready for it,” says Freeway, who had recently debuted on “1-900-Hustler,” a standout track from Jay Z’s The Dynasty: Roc La Familia. “I spent the entire week beforehand getting my bars together. My whole mind frame was: This is my platform, this is the first time the world is really going to hear me.”

The mood was celebratory inside Hot 97’s downtown Manhattan studios on that evening. Freeway and the future members of what would become Philly rap group State Property, along with Beanie Sigel and Memphis Bleek, popped bottles of Belvedere vodka, rolled Backwoods blunts, and rhymed over classic boom-bap productions (Mobb Deep’s “Quiet Storm,” Biggie’s “Kick in the Door,” and LL Cool J’s “I Shot Ya”) for nearly an hour of gripping radio. “It was the spark to their careers,” Cipha Sounds remembers. “Everybody was wondering about these guys afterwards. Everybody wanted to hear more from them.”

Jay Z executed the hardhat duties of a hype man throughout, chuckling at the hottest lines and punctuating verses with cries of “It’s the Roc!” He then thanked Flex and Tracy Cloherty for permitting what was dubbed “The Roc-A-Fella Takeover,” a talent showcase for the label that doubled as free advertising.

“That was a little unusual for me to have a bunch of unknown rappers freestyling,” Flex says today. “I probably wouldn’t have done it if it weren’t for Jay Z.” Because what was good for Jay Z was good for Hot 97—until it wasn’t.