The movie was filming scenes at 10th and Willow Bar this week, beginning Sunday, March 3.
The movieis a romance about two young men during World War I who embark on a journey to record the music and lives of American countrymen, according to a synopsis.
O'Connor played Prince Charles in "The Crown" and appears in the upcoming movie "Challengers", while Mescal recently won acclaim for his performance in "All of Us Strangers."
Director Oliver Hermanus told Gay Times his two co-stars are already "on fire".
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