There have been a number of news reports (one linked below) about a lawsuit filed against internet radio site Pandora by the big companies who are claiming copyright violation for classic rock songs.
This is an extremely important issue. Many people, having read that music recordings issued in the US before February 1972 aren't covered by US copyright law, assume that such recordings are in the public domain. But this suit claims that they are covered by US state copyright laws.
They are probably right. I'm not an authority, but I've read in reliable sources (books by Nolo Press) that due to state copyright laws and common laws, in fact no recorded music is in the public domain in the US.
The research I've done indicates that the copyright status of recorded music is a particularly chaotic and confusing area. I don't know if this lawsuit will clarify things, but anyone interested in the issue should be following it.
(An example of the confusion: suppose I buy second hand a CD issued in the 1980s by a now defunct company in Czechoslovkia which includes an unremastered recording taken off a 78 rpm recording made by an unspecified company in Greece in 1932. I put the recording from the CD on my desktop computer in the US, remaster it with software I have on that computer, and put my remastered version on a non-commercial publicly accessible web site. Have I violated copyright? Or, How do I know if I've violated coypright? Or, if I have or may have violated copyright permission, whom do I contact to get it? Try to get an answer to those questions.)