It’s 1986. Rap music is explosive and on the rise but still misunderstood and barely represented in the mainstream. The leading innovators are Run-D.M.C., a trio from Queens who sport black leather jackets and unlaced Adidas sneakers. Two albums into their career, Joseph “Run” Simmons, Darryl “D.M.C.” McDaniels and Jason “Jam Master Jay” Mizell are already minor stars and musical revolutionaries. For their third album, producer Rick Rubin, a 22-year-old white kid from New York University, comes up with a crazy idea: He recruits Steven Tyler and Joe Perry, the leaders of the down-and-out arena-rock group Aerosmith, to collaborate with Run-D.M.C. on a new version of their 1970s staple “Walk This Way.”

The rappers hate the idea. The rockers, struggling with drugs and low record sales, don’t know what to make of Rubin’s pitch. But on a Sunday in March, they meet in a Manhattan recording studio to create what will become one of the most important songs of the modern pop era. This is the oral history of Run-D.M.C.’s cover of “Walk This Way.” (Some responses have been edited for length and clarity.)