Kool DJ AJ Scratch

Kool DJ AJ Scratch, a pioneering hip-hop disc jockey who had been in the business since the late 1970s, died Wednesday, according to his friend and collaborator, the rapper Kurtis Blow.

“RIP to my DJ and friend Kool DJ AJ!!!!” wrote Blow on his Twitter account.

AJ Scratch’s age and cause of death weren’t released.

A native of New York’s Lower East Side, AJ Scratch, who was born Aaron Gerald O’Bryant, also helmed the turntables for Busy Bee. He eventually retired from the DJ business in 2010.

Blow paid tribute to the disc jockey in his 1984 hit, “AJ Scratch.”

Names big and small in the hip-hop industry offered their condolences on social media.

“DJ AJ a great pioneer in the rap game has passed away to today,” tweeted Russell Simmons, the business magnate and co-founder of the hip-hop record label Def Jam. “Amazing sweet spirited human being. God accept him into greater service.”

Grandmaster Flash, the leader of Grandmaster Flash and the Furious Five that performed during the 1970s, wrote on Instagram: “I put this Dj in front of my biggest crowds in the ’70s and he never let me down. …”

“RIP DJ AJ. Hip Hop Legend!” wrote Ice-T, the rapper and actor on TV’s “Law and Order.”

Kool DJ AJ — a pioneering hip-hop DJ working since the late 1970s — died Wednesday (Sept. 9), his friend and collaborator Kurtis Blow announced on Twitter.

AJ worked with Blow and Busy Bee throughout the ’80s and DJ’d in to the ’90s, retiring from hip-hop in 2010.

His exact age and cause of death are unknown. The hip-hop community mourned the loss on social media with tribute posts.