Any film told against the backdrop of the Holocaust presents a fragile proposition for film composers. Underlining the film’s emotions is key, but caution must be used to avoid overdramatizing a sensitive and horrifying moment in history.

James Newton Howard and James Horner took the leap this year in a pair of WWII films: Howard in “Defiance,” the fact-based story of the Jewish resistance in Lithuania, and Horner in “The Boy in the Striped Pajamas,” about the friendship between a concentration-camp officer’s son and a Jewish prisoner.

“One has to be careful, handling a delicate situation such as the Nazis and the Jews,” Howard says. “It’s a very sacred topic.” Notes Horner: “There are a lot of pitfalls doing an Auschwitz movie, lots of directions that you could go that are overused. I thought, ‘I’ll doom the film in the first 30 seconds if we choose the wrong color.’ It doesn’t matter what the notes are.”

For “Defiance,” Howard and director Edward Zwick decided to feature a solo instrument. Howard toyed briefly with using a cello, but they ultimately went with a violin and engaged Grammy-winning soloist Joshua Bell. “It seemed the instrument that best expressed, or related to, the soul of these people,” Howard says.

Howard found the violin “very intimate, very personal,” and often used it against images of the Jewish refugees on the move in the forest. “I sometimes wrote in a quasi-minimalist way, trying to keep the melody austere enough, moving but hopefully not overly sentimental,” he says.

Bell says he found the film “very powerful and quite intense.” They recorded in London’s Abbey Road studios, concerto-style, with Bell standing before the orchestra.

For “The Boy in the Striped Pajamas,” Horner chose a piano as the solo instrument and played all of it himself. “I wanted something neutral and very, very simple — something vaguely Germanic, with a classical feel to it, yet didn’t impart any color, as a clarinet or a voice would,” he says. “Keeping it simple and stark, that was as far as I dared go.”

The entire score was written for piano and strings, plus two oboes and two barely heard French horns. The story, he felt, needed very subtle handling, with tone shifts only “by millimeters. At every turn, it was almost better not to have music, because just having music meant I was making some contribution that made the emotional state gloomier.”

Late in the film, the score undergoes “a whole transformation,” Horner explains, “from having very little forward momentum to suddenly becoming panic,” reflecting what’s happening onscreen. So for the end titles, Horner played the main theme as a lullaby, “in its simplest version, with no ornamentation. It just goes on and ends wistfully,” he says, providing an emotional release for viewers.