Interestingly enough, a theme for Leonard was one of the very things composer Herdís Stefánsdóttir (“The Hate U Give”) wrote when she got the job. In an interview with /Film’s own Jack Giroux, Stefánsdóttir called it “beautiful and melancholic,” reflecting this character who believes himself to be a force for good, which admittedly doesn’t seem very accurate on a surface-level examination of the scene in front of audiences. A big dude with a crude weapon tying up two dads and their little girl isn’t what you’d expect from someone who thinks they’re the good guy.
Stefánsdóttir describes the character as having a heavy burden “and the theme I wrote for him resulted in his acceptance of that, but we actually didn’t end up using that in the film.” She went on to explain exactly why.
“After I had written some character things before seeing the movie, we understood that we had to take another direction in the film, because a big part of the plot is that we cannot reveal who Leonard really is. That has to wait. So we cannot reveal anything about the characters with the music. There couldn’t be a real profound character theme for Leonard or something that tells us about who they are, because it’s so important that we don’t know, and the music doesn’t tell that.”
In short, a theme for Leonard would either tip the story’s hand way too early or feel incredibly deceptive, so the decision was made to axe it completely.