What is NEEDED is a "use it or lose it" clause!
That is, any sound recording which is NOT regularly available fron its
"copyright owner" for a period encompassing 365 days or longer falls
into the Public Domain!
It is rather discouraging to know that IF someone happens to find
Edison's "tin-foil" recording of "Mary Had a Little Lamb" and then
carefully flattens it out to a point of "playability"...they could NOT
then reissue it for another 50 and a fraction years...according to
Mr. Bono's "Eternal Copyright" law...?!