I hope there is someone here who might answer (while not being legally accountable for their answer - I mean I still hope the answer is correct but I don't take it as legal advice).... 

I am looking at three questions:

(1) are audio materials copyrighted for the same amount of time as printed materials? (are the terms and dates for both mediums the same under U.S copyright law?)

(2) I am looking at title 17 USC circular 92 chapter 3 section 303 (b) ( which says:

"The distribution before January 1, 1978, of a phonorecord shall not for any purpose constitute a publication of any musical work, dramatic work, or literary work embodied therein."

So, If I understand this "plain english"; distribution of a work does not mean that it is "published". Are "circulation" and "publishing" two categorically separate ideas under copyright law? ... or am I mis-reading this text? 

(3) If I have audio from before 1978 and it was never formally published (like many field recording from linguists and researchers), my understanding is that I could formally publish it now and it would enter copyright in 2014 (now). But if I just circulate the audio work now, I guess that does not constitute a publication of the work? is that right? So, how do I know that digitization and distribution of the content from an institutional archive is not "publication" and is just "circulation"?

- I am sure that I have some assumptions in here which are mis-guided. please feel free to set those straight. 

- hugh