Because protection is automatic even without registration, a common law notice would be no different from any other: Copyright © [current year] [creator or owner's name].
Prior to 1989 is was necessary to display a copyright notice in order to maintain protection on a work. That year the US signed the Berne Copyright Convention which standardized copyright law across national borders. One of the provisions that Berne contained was that a copyright notice would no longer be required. US law was amended to bring it into compliance.
In the US, since copyright law was amended in 1989, it has not been necessary to display a copyright notice for protection.
Just because there is no copyright notice evident a work is not free to use without permission. In 1989 current copyright law was amended, removing the necessity for a copyright notice to maintain protection. If you have a question about material you would like to use it's always best to ask first.
Under US copyright law, there are no recordings that are public domain; they are either covered under state copyright law prior to 1972, under federal copyright law if published after that, and under federal copyright law if they were never published at all. The only possible public domain records would be some that were published before 1989 and after 1972 without the necessary copyright notice or registration.
Generally, at least under US Law, copyright protection extends 70 years past the death ot the author/creator of the work.
Yes it, in all likelihood it is an infringement of copyright. Whether or not a copyright symbol is displayed has no bearing on the materials copyright status. Since the law was amended in 1989 it has not been required to have a copyright notice in evidence to maintain protection.
It varies from country to country. In the US, the Copyright Office is currently (January 2012) considering whether to federalize pre-1978 sound recordings, which are frustratingly covered only by state law at this time. US federal copyright law currently (2012) covers sound recordings produced after Feb 15, 1972. Any sound recordings published from 1972 to 1978 are public domain (no copyright at all) unless they had proper copyright notice upon publication. If they had proper copyright notice, they are copyrighted under federal law for 95 years.
The copyright notice and other cataloging data is usually on the reverse of the title page.
Under US law a copyright notice has not necessary since 1989, for a work to be protected
Same as copyright notice for anything else: Copyright, or copr. or circle-C, the date of copyright and the author or other copyright owner's name. E.g., "Copyright 2012 Walt Disney Productions, Inc."
Legally, nothing. There is no requirement to have a copyright or trademark notice in order to establish intellectual property rights and hasn't been since 1989 when copyright law was amended to bring it into alignment with the Berne Copyright Convention.
It can be. Notification is not required for protection.