Postproduction refers to the time in the movie production when the shooting is done and the film is undergoing editing which requires the help of editors and composers. Common agreements needed during this time period include editor agreements and composer agreements.
Like actors, editors and composers may belong to a guild or union which can impact the nature and complexity of their agreements. However, the agreements will typically include the term of employment, the rate of employment and should also address who will own the finished product.
Editors are usually hired on a “work-for-hire” basis, which enables the producer to maintain ownership of the edited product. Often, compensation is divided based on the number of times the film needs to be edited or the number of compositions that are required to be written by the composer.
It is not uncommon for a film to use many editors at a time and it is therefore important to split the agreement up in this manner to ensure that the producer can continue to hire more editors as needed.
It is also critically important for the success of a film to use music and other sound to create sound effects. It is equally important to use clips of film and TV to enhance the overall presentation of the movie. This is a very complex area of filmmaking and unsurprisingly involves even more types of agreements, clearances, and licenses, such as sync agreements.

Excerpt Source: FilmDaily.tv