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.
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.
[…] The different state laws vary quite a bit, and apparently a bunch of them do exempt personal use from those laws.
http://www.techdirt.com/articles/20100804/02405510490.shtml