Everybody knows what the adults sound like in a Peanuts cartoon. Wah-WAH-wah-WAH-wah-WAH-WAH — or something along those lines.

There's a good reason it sounds like a brass horn: from the beginning, any time adults "spoke" on-screen in a Peanuts cartoon, their indecipherable voices came from a trombone. So, when Blue Sky Studios set out to make the first Peanuts big-screen movie in some 35 years — and the first to ever render Charles Schulz's iconic characters using computer animation — director Steve Martino decided that, despite its updated veneer, everything about it had to be authentic.

That meant using a trombone for the adult voices once more, and not just any trombone or player would do. Martino turned to the musical prodigy known as Trombone Shorty. The 29-year-old New Orleans native, born Troy Andrews, came to the production with "a little arsenal" of instruments and accessories like plungers and mutes. Martino told Mashable that it took a while to find the combination that provided the right sound.

For the movie, the filmmakers wrote actual lines for the adult characters, knowing that those lines would never be heard in a spoken voice. Instead, Shorty was tasked with turning those words into wah-wahs with his trombone.

He did such a great job on the film that a Web app was made using new Trombone Shorty recordings to turn anything you say into Peanuts adults' "wah-wah"s. It's called "The Wah-Wah Machine," and it can be found here.

The Peanuts Movie lands in theaters on Nov. 5, 2015.

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