Iron Maiden's new two-LP set The Book of Souls includes a song that singer Bruce Dickinson sees as a sort of tribute to Robin Williams.

Dickinson discussed the track, titled "Tears of a Clown," during an interview with the Italian publication Corriere Della Sera (via Consequence of Sound). "My favorite song is one I didn’t write," he explained. “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."

The Book of Souls, due Sept. 4, arrives just a little over five years after the group's previous studio effort, The Final Frontier, and caps a turbulent year for Dickinson, who recently battled a cancer diagnosis.

As Dickinson told Corriere Della Sera, he realized something was wrong when a "strange ball ... the size of an apricot" showed up on his tongue. "In the first five minutes you wonder: Why me? Then reflect and change the question: Why not? Gradually accept and respect the opponent. To beat it."

Dickinson also reaffirmed plans to begin what's being referred to as a two-year tour in support of The Book of Souls in 2016 and delved into the historical inspiration for "Empire of the Clouds," the 18-minute closing track he penned for the album, saying the song tells the story of the British airship R101, which crashed during its maiden overseas voyage in 1930.

Iron Maiden have completed a video for "Speed of Light," the first single from The Book of Souls, which is out now.

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