As HBO's Watchmen continues to gain ground, the soundtrack for the television superhero drama contains a surprising nod to one other than DC Comics' Superman.

Trent Reznor and Atticus Ross' soundtrack is set to be released across three volumes, the first of which went on sale earlier this week. The second track of Volume 1 sticks out, as it is titled, "Orphans of Krypton" -- a reference to the Man of Steel's home planet.

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The album description on Nine Inch Nails' website states, "Created in collaboration with the show's writers, each LP features the score from Academy Award winners Trent Reznor and Atticus Ross as well as artwork and packaging exclusive to this vinyl release that explores the culture of Watchmen America and provides revealing insights into the saga's mythology and mysteries."

The soundtrack draws upon the themes of the series, with each volume being released as the first season progresses. Volume 1 was released on Nov. 4, with Volumes 2 and 3 set to go on sale Nov. 25 and Dec. 16, respectively.

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Developed by Damon Lindelof, HBO's Watchmen stars Jeremy Irons, Regina King, Don Johnson, Tim Blake Nelson, Louis Gossett Jr., Yahya Abdul-Mateen II, Tom Mison, James Wolk, Adelaide Clemens, Andrew Howard, Frances Fisher, Jacob Ming-Trent, Sara Vickers, Dylan Schombing, Lily Rose Smith and Adelynn Spoon. The series airs Sundays at 9 p.m. ET/PT.