How did King Vidor use postsynchronization in Hallelujah?

In his 1929 film Hallelujah, King Vidor utilized postsynchronization to overcome the technical limitations of early sound recording, which typically required simultaneous capture of image and audio.1

For a sequence depicting the hero being chased through Arkansas swamplands, Vidor filmed the action on location without recording sound, which allowed him to use a freely moving camera. Later, in a studio setting, he added a separately recorded sound track to the footage. This track incorporated both naturalistic and impressionistic sound effects, demonstrating that the sound track could be manipulated independently of the visual image. This technique helped resolve the era's debate over the necessity of synchronous, "naturalistic" sound recording, eventually becoming a standard industry practice.1