The hip-hop community has lost another pioneer. Kool DJ AJ passed away today (Sept. 9). The sad news was confirmed by rapper Kurtis Blow, a longtime friend of AJ, who served as the rapper's DJ throughout his career.

Blow shared the news of AJ's sudden passing on Twitter. "RIP to my DJ and friend Kool DJ AJ!!!!" he wrote. There is no official word on the cause of death.

The Bronx, N.Y.-bred DJ worked behind the turntables for both Busy Bee and Kurtis Blow in the early ‘80s and deejayed through the ‘90s until he retired in 2010. AJ was also a promoter alongside fellow hip-hop legends DJ Kool Herc and Pete “DJ” Jones.

But Kool DJ AJ will most likely be remembered for his contributions with Kurtis Blow. He was the first DJ to break Blow’s first hit song, “Christmas Rappin’” in 1979, and wrote his classic 1985 tune, “If I Ruled the World.”

However, many rap heads will remember DJ AJ for his funky track "AJ Scratch," from Blow's 1984 album, Ego Trip. The song has been sampled several times by such artists as Run-D.M.C. ("You Be Illin'"), Public Enemy ("Welcome to the Terrordome") and DJ Shadow ("The Number Song").

Upon hearing news of AJ's passing, DJs like Premier and Funkmaster Flex and rappers like Ice-T went on Twitter to send out their condolences.

Kool DJ AJ was a true pioneer in hip-hop and will be sorely missed. We send our sincerest condolences to his family and friends. Rest in peace.

Listen to Kurtis Blow's "AJ Scratch"

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