It is a bit confusing but here you go Howard.. " How long copyright in sound recordings lasts
The length of term of copyright in a sound recording depends on whether or not it has been published (released) or has been communicated to the public (for example, played on the radio)

if a recording is not published or communicated to the public, copyright lasts for 50 years from when the recording was made

if a recording is published within 50 years of when it was made, copyright lasts for 70 years from the year it was first published

if a recording is not published within 50 years of when it was made, but it is communicated to the public, copyright lasts for 70 years from the year it was first communicated to the public

if a recording is first communicated to the public within 50 years of when it was made and is then published at a later date (but within 70 years of its first communication to the public), copyright lasts for 70 years from the year it was first published"   

I hope that clarifies the difference. But pre-1963 is a cut off point, as the act didn't apply. Hence a whole load of golden oldies compilations with rock n'roll hits that may occasionally include the Beatles 'Love Me Do', but not 'She Loves You'. It used to be a straight 50 years for all recordings, but they extended it to 70. But unpublished tapes are 50 years. Hence Apple released some rarities on the Internet for a short period and removed them, to be able to say they had 'published' them and give themselves a reserve stash of material that would have been out of copyright.