Watch Ethan Hawke and Tom Hiddleston Nail an Impromptu Duet

In Born to Be Blue, Ethan Hawke plays singer and trumpet player Chet Baker, known to many as the “James Dean of Jazz.” In I Saw the Light, another musically-oriented biographical drama out now, Tom Hiddleston plays country music icon Hank Williams. But Hawke thinks perhaps the actors should have swapped places. Whereas he plays the guitar and grew up with a father who collected the sheet music of Hank Williams songs, Hiddleston plays the trumpet and grew up with a mother who cooked to the sounds of Chet Baker. “I really should have been cast in your part,” Hawke told Hiddleston, “and you should have been cast in mine.”

Put the two men in a room and you’re all but guaranteed to get a duet. Within moments of meeting in TIME’s studios, the pair launched into a spiritual rendition of the song from which Hiddleston’s film takes its name, then seamlessly segued into a huskily Baker-esque performance of “My Funny Valentine.” But it was in their discussion of the preparation behind those tunes that the actors found the most similar notes.

Though their movies diverge in form—the unconventional Blue takes liberties with the facts of Baker’s life whereas Light hews closer to the traditional biopic formula—they faced similar challenges in learning to sing and play like the legends they portray. “When you’re playing a cop, you don’t really have to arrest somebody, you don’t really have to shoot somebody,” says Hawke. “But when you play a musician, you have to play.” And it’s not sufficient to simply open your mouth and sing, says Hiddleston. “You have to transmit the power of the song of an icon.”

It’s a tall order, and the pressure is not dissimilar, says Hawke, to that which accompanies the performance of a Shakespearean soliloquy. “People come see Macbeth, they have an expectation that they’re going to be blown away. So if you’re anything short of that then you stink. And if I’m going to go see Hank Williams play, you better blow me away,” he joked—though he repeatedly emphasized that Hiddleston did just that.

The actors both felt that another year (or ten) would have helped them in their parallel quests to scratch the surface of the musical abilities of the musicians they play. But verisimilitude only goes so far. “What you don’t want to do is imitate,” says Hawke. “You want to find, how the hell do I relate to this person? If you get into imitation then you’re not really listening.” Hiddleston agrees. “It becomes an act of interpretation. You’re always interpreting other people’s truth.”