Unpublished works are treated differently from published works under US copyright law. As of 2010, it is not known whether the use of music in a film constitutes publication of the music for the purpose of copyright. The use of music in a film can cause uncertainty with regard to copyright. Experts in the field of public domain sometimes differ in their opinions as to whether a particular film is in the public domain. A film can lose its copyright in some of those elements while retaining copyright in other elements. It is difficult to determine the public domain status of a film because it can incorporate any or all of the following copyrightable elements:
There is no official list of films (or other works) in the public domain.
