Veteran ADR mixer David Boulton has some 225 film and TV credits, including such high-profile projects as “The Wolf of Wall Street,” “Life of Pi,” “Planet of the Apes” and “Crouching Tiger, Hidden Dragon,” but it’s his long-running collaboration with Spike Lee that’s arguably his most impressive accomplishment.

Boulton began working with Lee back in the ’80s on “School Daze” and has worked with the director ever since. Their latest collaboration, Cannes Grand Prix winner “BlacKkKlansman,” about an African-American detective who infiltrates the Ku Klux Klan, is set for release Aug. 10 by Focus Features.

“We’re both about the same age, and we’re both from New York,” says Boulton of their relationship. “We’re like a well-oiled machine by now. I love working on his projects because he loves sound and really understands it.”

Lee says sound is “hugely important” in all his films. “I’m very involved, and I always put as much as emphasis on sound and music as I do on the acting and editing and cinematography and so on,” he says. “It’s absolutely crucial, and ADR is a big part of that.”

Automated dialogue replacement, the practice of re-recording dialogue in a studio in synchronization with the picture, isn’t something actors love doing. Boulton points out that ADR can occur six months after the shoot. “And you’re not that character anymore,” he explains. “You’re not on set with all that adrenaline, yet you’re trying to match the original performance — and make it even better if possible.”

The director’s coaching helped the process. “Spike was at all the sessions, directing the actors and making it all as fun and easy as possible for them,” says Boulton.

The sessions were mainly held at C5 Sound in New York. For the handful that had to be completed in Los Angeles, the director sometimes traveled
but sometimes stayed in his home
base of New York and collaborated remotely, listening in and monitoring the work. Lee, says Boulton, took his trademark passionate approach to the film’s material.

“One of the big challenges was keeping dialogue topical, as it’s set in the ’70s,” says Boulton. “We had to pay very close attention to the language and phrases that people used back then, including all the slang. And Spike finds humor in stuff you wouldn’t expect him to, like racial slurs.”

Boulton notes that the film’s outdoor scenes needed more ADR than did the indoor ones. “You usually have problems with production sound because of traffic and other noise,” he says. “And crowd scenes, like those outside the courtroom, needed work.”

Another challenge was just keeping it simple, he adds. “You want to maintain the original performance, and depending on the angles and shots in a scene, you can go in and
work on just a phrase or even a word,” he says. “ADR is a necessary evil of the movie business, and it’s been around forever. In the old days we’d redo entire scenes, but we’re far better at it now. When it comes to ADR, less is definitely more.”