The claim that "pre-1923 works are in the public domain" is correct only for published works; unpublished works are under federal copyright for at least the life of the author plus 70 years. For a work made for hire, the copyright in a work created before 1978, but not theretofore in the public domain or registered for copyright, subsists from January 1, 1978, and endures for a term of 95 years from the year of its first publication, or a term of 120 years from the year of its creation, whichever expires first.[4] If the work was created before 1978 but first published on or before December 31, 2002, the work is covered by federal copyright until 2047.
Works published with notice of copyright or registered in unpublished form prior to January 1, 1964, had to be renewed during the 28th year of their first term of copyright to maintain copyright for a full 95-year term
Until the Berne Convention Implementation Act of 1988, the lack of a proper copyright notice would place an otherwise copyrightable work into the public domain, although for works published between January 1, 1978 and February 28, 1989, this could be prevented by registering the work with the Library of Congress within 5 years of publication. After March 1, 1989, an author's copyright in a work begins when it is fixed in a tangible form; neither publication nor registration is required, and a lack of a copyright notice does not place the work into the public domain.
Sound recordings fixed before February 15, 1972, were generally covered by common law or in some cases by statutes enacted in certain states, but were not covered by federal copyright law. The 1976 Copyright Act, effective 1978, provides federal copyright for unpublished and published sound recordings fixed on or after February 15, 1972. Recordings fixed before February 15, 1972, are still covered, to varying degrees, by common law or state statutes.[6] Any rights or remedies under state law for sound recordings fixed before February 15, 1972, are not annulled or limited by the 1976 Copyright Act until February 15, 2067.[7]