When Def Jam co-founder Rick Rubin suggested Run-DMC record their own version of Aerosmith's "Walk This Way," the legendary hip-hop group had heard of neither the band nor the song. He ultimately convinced the trio it would help them crossover into the mainstream - but it wasn't easy.

"I went through my whole album collection trying to find a song that Run-DMC could do that would point up their relationship between hip-hop and other kinds of music," said Rubin, who co-produced the song along with Russell Simmons. "'Walk This Way' had a familiar rock sensibility to it, but at the same time with very little change, would function as a hip-hop song."

But the Queens, N.Y., band wasn't convinced. They'd heard the beat off of Aerosmith's 1975 record at clubs but never knew its origin. "All the DJs would scratch out the names and the titles (from the records they used)," Darryl "DMC" McDaniels explained, "so nobody could look and see, 'What's that beat?'"

Run-DMC reluctantly agreed to give "Walk This Way" a whirl, but initially started rapping their own lyrics over the familiar beat. "And Rick said, 'no, make the whole thing over,' Joseph "Rev. Run" Simmons said. "'Huh? These aren't even rhymes. I don't even know what he's saying.' So we had to go home with the record, and study it."

And they did. But the study session wasn't a quick fix. "How are we going to make this record over when we have never even heard what the vocals sound like?" McDaniels said. "We heard, this is what me and Run called it, 'hillbilly jibberish.' This is how it sounded to us. [imitating jibberish on the song] ... To this day a couple of words are wrong because we didn't know what he said there.

"Me and Run thought Russell and Rick were trying to ruin us," he added. But they recorded it nonetheless, with assists from Aerosmith's Steven Tyler and Joe Perry, and it appeared on their third record, Raising Hell, that year.

Instead of ruining them, the new version of "Walk This Way" showed how music could transcend genre boundaries. Both rock and hip-hop radio DJs played the song. The record went triple platinum, reaching No. 4 on the Hot 100, and in 1987, it earned Run-DMC and Aerosmith a Soul Train Music Award for Best Rap Single. The album, it was recently announced, will be added to the Library of Congress' collection of "culturally, historically or aesthetically significant" works. It also helped revive Aerosmith's career by both putting them back in the spotlight and opening their eyes to the idea of collaborating with other songwriters.

"It took our thing to some new eyeballs," Run recently admitted in Uncut. "At that moment, was it our favorite thing to do? No, we were happier doing 'My Adidas' and 'Peter Piper,' but Rick (Rubin) knew that this would be something special."