ITT we post everything that falls under public domain, I start :
A must see
>Night of the Living Dead
"Why is this film in the public domain?
In 1968, US copyright law required copyright ownership to be displayed on the actual print of a film (e.g. in the credits). Early prints of Night of the Living Dead had the title Night of the Flesh Eaters, under which was the copyright information. When the title was changed for theatrical release, the distributors apparently failed to include the copyright information - leaving the film uncopyrighted and in the public domain. This also explains why there are so many different VHS and DVD recordings."
That's how it works now, but not how it worked in the 60's. And for any work, the copyright law that's active during its completion is what matters, not whatever law gets passed later.
Film student here, and not sure about back then but nowadays you need to get everything copyrighted; it doesn't matter how much proof you have, if it's not copyrighted you've got no legal ownership. Something as simple as a change of title could very easily screw you over
Who gave you that legal advice? If it was your lawyer, you should fire him. Or anyone who's taking your money to "self-copyright" your works.
You can REGISTER a copyright, but that's only needed if you expect someone will challenge your authorship or the claimed date of creation. Certainly not needed for copyright protection as such.
Anything anyone creates, music, art, writings, whatever, is automatically copyrighted. Unless you actively waive that copyright by placing the material in the public domain.