See http://copyright.gov/docs/sound/
"Although sound recordings were first given federal copyright protection in 1972, sound recordings made before February 15, 1972 remained protected under state law rather than under the federal copyright statute. As a result, there are a variety of legal regimes governing protection of pre-1972 sound recordings in the various states, and the scope of protection and of exceptions and limitations to that protection is unclear. Current law provides that pre-1972 sound recordings may remain protected under state law until February 15, 2067. After that date they will enter the public domain."