The president and first lady sent a letter to the family of fellow Chicagoan Frankie Knuckles, the DJ known as the “Godfather of House” who died last month at age 59 from diabetes-related complications.

It was posted on the Facebook page of DJ David Morales, Knuckles’ friends and business partner at Def Mix Collective.

“Frankie’s work helped open minds and bring people together,” President Obama wrote. “Blending genres to capture our attention and ignite our imaginations. He was a trailblazer in his field and his legacy lives on in the city of Chicago and across the globe.”

When he was a senator, Obama had Aug. 25 declared “Frankie Knuckles Day” in Chicago, which named a street after him.

“Frankie’s memorial service was emotionally special,” Morales wrote. “To have his friends, family and the Governor speak about Frankie goes to show the impact he has had on people. You know you’re a TRUE LEGEND when u get one of these…”