In the past, we've pointed to the excellent (and useful) public domain tracker from Cornell, which helps you determine whether or not a work is in the public domain. In the past, I've generally focused on the top part of the chart, and forgot the ridiculous situation with sound recordings, which gets very little attention when it comes to copyright discussions. Basically, due to a quirk in the way US copyright law was constructed, sound recordings made prior to 1972 are treated quite differently than other works. I was reminded of this, thanks to Glyn Moody, pointing me to a discussion on an archivists' mailing list about the trouble of using World War I music. As copyright law stands today, works (in the non-sound recording division) published prior to 1923 are in the public domain. But that's not true for sound recordings: The bad news is that no sound recording made before 1972 has federal copyright protection. They are instead protected by state common law copyrights, and will not enter the public domain until in most cases 1 January 2049, regardless of when they were recorded. . Note that state protection is afforded even to European recordings, most of which enter the public domain in their home country after 50 years. Understanding why this is really does highlight just how screwed up copyright law has become in this country, and how far it's come from its origins. That same discussion points people to Peter Jaszi's (a true expert on copyright and fair use) recent paper on pre-1972 sound recordings, where he details the history of all of this. In part, it's due to the fact that Congress did not include sound recordings in the 1909 Copyright Act. It's actually quite important to understand why they did not do so: Although Congress subjected federal copyright protection to an overhaul by enacting the 1909 Copyright Act, it still failed to grant statutory copyright protection to sound recordings. Despite efforts by some members of Congress to raise the issue of sound recordings, the final bill declined to extend protection. Indeed, the report released with the Copyright Act expressly stated that Congress did not intend to protect sound recordings: "It is not the intention of the committee to extend the right of copyright to the mechanical reproductions themselves, but only to give the composer or copyright proprietor the control, in accordance with the provisions of the bill, of the manufacture and use of such devices." According to one commentator, Congress had two principal concerns about sound recordings, leading it to decline to protect them. First, Congress wondered about the constitutional validity of such protection. The Constitution allows Congress to protect "writings, " and Congress was uncertain as to whether a sound recording could constitute a writing. Second, Congress worried that allowing producers to exclusively control both the musical notation and the sound recording could lead to the creation of a music monopoly. That seems like an important paragraph to show to folks who insist that copyright on sound recordings must obviously be covered by copyright and/or that it's a "natural right" to include sound recordings under copyright. Clearly, even Congress felt it was likely to be unconstitutional for quite some time.
Congress (under tremendous pressure from exactly who you would imagine) finally added protection to sound recordings in 1972, but in the meantime, some states had passed local laws to deal with unauthorized copying and distribution of sound recordings. While Federal Copyright law in the 70s was designed to totally pre-empt state copyright laws, a court ruling in Goldstein v. California (over bootlegging) found otherwise - and said that state laws did apply to sound recordings published prior to 1972. The different state laws vary quite a bit, and apparently a bunch of them do exempt personal use from those laws.
But, either way, because of this little quirk of history, where Congress mostly believed that sound recordings could not be subject to copyright on a Constitutional basis, many such works are effectively locked up for much, much long than they would be if under federal copyright law.