drew from the works of those who have come before them, and that preserving such rights indefinitely would stifle creativity. One thing that has certainly changed since 1709 is the term of copyright; US copyright eventually settled on a period twice as long as the Statute of Anne (28 years, renewable for 28 more years); revisions to this law in the past three decades have extended these 56 years to 80, 100, and even as many as 120 years; the last of these, the "Sonny Bono Copyright Extension Act," went further and even re-instated copyright in works where it had become extinct, freezing the date at which works could enter the public domain at 1923. Many creative artists feel that this law has exercised a stifling effect upon creativity; many of them joined in support of a legal case, Eldred vs. Ashcroft, that challenged these extensions on the basis of the Constitution's reference to copyright law being for a "limited term." The Supreme Court eventually ruled against Eldred, saying in effect that Congress could establish any length of term they wanted, so long as it was not infinite. Could, is of course, not should.
The result has been, ironically, that in the very age when the ability of writers, artists, and musicians to draw upon, alter, and incorporate what the copyright office calls "previously existing works" is at its greatest, the legal barriers against doing so have been raised to the harshest and longest in the history of copyright protections. This is offset, to a degree, by two factors: 1) "fair use," a doctrine established in the 1977 revision of the law, whereby a certain limited amount -- say, less than 10% of the original "work" -- may be used so long as it is not employed for profit, is used in an educational context, and/or used spontaneously; and 2) simple lack of enforceability. It's quite impossible to police all the billions of web servers, web pages, and personal computers and devices, to ensure that no copyrighted material has been taken or stored; enforcement, as a result, tends to be spotty if dramatic (as in the case of a woman in the midwest who was assessed a fine of 1.5 million dollars because her son had shared 24 music files on his Napster account).
It needs to be noted that copyright also functions very differently depending on the medium in question. Printed texts are straightforward enough, but in the case of physical media such as a sculpture or a painting, possession of the physical object confers certain property rights, including the right -- if one desires -- to restrict or prohibit "derivative" works such as photographs of these works, although the issue of non-manipulated or "slavish" copies is a murky one. Music is the most complex form: there are at least four layers of copyright in a recorded song: 1) The composition itself, and its embodiment in sheet music; 2) The performance of that composition on the recorded matter, including the act of interpretation and any variations on the composition; 3) The physical embodiment, if any, of this performance, known as "mechanical" rights; and 4) The right to transmit the performance. All of these, of course, were once separate domains: the sheet-music industry/print, the recording studio, the record company or "label," and radio stations -- but all are now merged indistinctly into a single, complex activity that can all be achieved on a single device, even a smartphone.