Complex sentence: There was initially some doubt among the animators that a sound cartoon would appear believable enough, so before a soundtrack was produced, Disney arranged for a screening of the film to a test audience with live sound to accompany it.
Split into simpler sentences: There was initially some doubt among the animators that a sound cartoon would appear believable enough. So before a soundtrack was produced Disney arranged for a screening of the film to a test audience with live sound to accompany it.