Studio System.

In the traditional, old-fashioned studio system, every aspect of production was in one place-- from the actual production of the screenplay to the film to the editing. This is interesting because the different film companies were therefore completely vertically integrated. This affected the films that were made because oftentimes the companies were linked to their own specific genre (Ex.: MGM = the musical). Long-term, this set the foundation for the different kinds of genres that are alive today. We still see detective films and comedies, all genres that developed from this studio system. Take the musical as an example. Because MGM had developed it from the beginning a certain way, there's a set of criteria that it follows in order to qualify as a musical and since that time, we've been able to develop it into what it is today.