When Gary Rizzo and Jonathan Greber signed on as part of the sound team for the documentary, “Laurel Canyon,” they began a massive undertaking of matching sounds to people and remixing old recordings to make it acceptable to a modern audience. It starts on the side of Greber, the sound editor, who’s dealing with his team as well as the picture editor and a mountain of archival material. “There were some challenges of matching people when they were younger to when they’re older. We had to play around with those things but all the while making sure never to alter anything,” explains Greber. When the audio made its way over to Rizzo, the mixer, he had to make it work all these songs work in a modern sense even if they weren’t recorded to the effect. “You’re trying to make it into what is acceptable to a contemporary audience.