THE STORY OF NEW YORK hip-hop’s 1990s championship years is in many ways the story of rapper-executive dream teams, pairings that shaped the sound of the city and, after that, the world. The Notorious B.I.G. and Puff Daddy, Jay-Z and Damon Dash, Ja Rule and Irv Gotti — all of these partnerships made the behind-the-scenes swami as crucial a hip-hop figure as the rappers they helped mold.

For ASAP Rocky, the Harlem rapper whose debut album, “Long.Live.ASAP” (Polo Grounds/RCA), just made its debut at No. 1 on the Billboard album chart, that partner is ASAP Yams, his longtime friend, collaborator and co-owner of the ASAP Worldwide label.

But you won’t find Yams behind the mixing boards in a studio, or in a corner office at a record label laboring over marketing plans, or huddled with designers creating a fashion line. Just 24 years old, he exerts his pull in extremely nebulous fashion. ”Rocky’s like Luke Skywalker, and I’m Yoda,” Yams said, cackling a bit, one recent afternoon in the South Bronx office that serves as a hangout space for the ASAP crew and where Yams lingers when not at the neat apartment he’s long shared with his mother in the Riverdale section of the Bronx. Rocky may be a natural star, one of the most charismatic figures in contemporary mainstream hip-hop and the one with the most expansive approach to his music. But his road to the top was paved with the help of Yams, who is a spirit guide, a muse, a curator of sonic ideas.

Much of what you hear in Rocky — a fully assimilated take on hip-hop styles from across the country and from across time periods — can be traced back to Yams, who spent his formative years studying the genre, then learning how to transmit his taste to others. Hip-hop has long been obsessed with fealty to a specific place and time, and Yams’s vision of the genre as an open house, not a fortress, qualifies as a radical one.