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Metal legends Iron Maiden drop their 16th studio album next month, and it features an unexpected tribute. One of the songs off The Book of Souls—the band’s first double album—is named “Tears of a Clown” and honors the late Robin Williams, who died in August 2014.

“My favorite song is one I didn’t write,” frontman Bruce Dickinson told Italian publication Corriere Della Sera. (The song was written by the group’s Adrian Smith and Steve Harris.) “It’s ‘Tears of a Clown,’ which talks about Robin Williams. I ask myself how could he be so depressed when he always seemed to be so happy.”

Hear “Tears of a Clown” in full when Iron Maiden releases The Book of Souls on Sept. 4. The album’s lead single, “Speed of Light,” debuted earlier this summer.