I find it ironic that the first audio editors were able to cut visually, by following the audio waveform on the optical soundtrack, more than seventy years ago. It wasn't until the late '70s or so that DAWs became sophisticated enough to display a visual waveform that we finally regained this ability that we take for granted today.
In 1929, Max Fleischer produced Finding His Voice, an animated demonstration of the Western Electric Sound System (later known as Westrex), which employed optical variable area recording technology. This was a marked improvement over Vitaphone, which was a sound-on-disc system.
Link, via dvguru.com.
For those of you who wish to download a higher quality clip, you may find different versions available via the Internet Archive.