President Obama and First Lady Michelle Obama have honored the late DJ Frankie Knuckles in a letter they wrote to his family.

The letter was made public by Knuckles’ good friend and business partner, David Morales, who posted it to his Facebook page. “You know you're a TRUE LEGEND when u get one of these….” he wrote.

image via Facebook from David Morales

In the letter, the Obamas tell their fellow Chicagoans, “Frankie’s work helped open minds and bring people together. 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.”

Knuckles, known the “Godfather of House,” passed away due to complications with diabetes. When President Obama was governor of Chicago, he named Aug. 25 “Frankie Knuckles Day” and also named a street after him.

Knuckles passed away last month at the age of 59.