Yet because the copyright term is now so long, in many cases extending well over a century, most of twentieth century culture is still under copyright–copyrighted but unavailable. Much of this, in other words, is lost culture. No in is reprinting the books, screening the films, or playing the songs. No one is allowed to. In fact, we may not even know who holds the copyright. Companies have gone out of business. Records are incomplete or absent. In some cases, it is even more complicated. A film, for example, might have one copyright over the sound track, another over the movie footage, and another over the script. You get the idea. These works–which are commercially unavailable and also have no identifiable copyright holder–are called “orphan works.” They make up a huge percentage of our great libraries’ holdings.
– James Boyle, The Public Domain, 9.