L.A. musician Terrence Martin sat down with NPR to gush over the untitled song that was prepared just a day before Kendrick Lamar rocked the Colbert Report. Martin says that a portion of the performance was improvised because he and Thundercat “forgot the arrangement.”

“We came with that the day before at rehearsal,” Martin says, “[Because] we didn’t want to do nothing that’s already been done. He didn’t want to do ‘i.’ Let’s just, you know, fly out. Let’s rehearse in New York and get that energy and do something a little different.” Martin went on to say, “We had an idea of it a while ago,” he says. “But we wasn’t sure—but most of that was done right there—not right there but the day before. And then something magical and spiritual happened there to where some things that wasn’t, you know, rehearsed, happens… because I think me and Thundercat forgot the arrangement and just do what jazz musicians do. And Kendrick, him being like a horn player, he’s like Coltrane, man. Mild-mannered, soft-spoken, always practicing. New harmonic approaches, different techniques, falls in—there’s not a mistake on that stage with him. If the turntables fall, he gon’—like, it’s weird. It’s like water.”

For more listen to the full interview below:

Check the video below for Kendrick’s full performance: