The Record Group at the National Archives for the Office of War Information is 208:
There is a large collection of wartime broadcasts and recordings that is mostly not included in the online database:
The records of the United States Information Agency would also be worth looking at since recordings from World War 2 are in there, too. That is Record Group 306.
Check with the Roosevelt and Truman Presidential Libraries as well since there would have been communications between the OWI and the White House.
> On Sep 4, 2019, at 10:28 AM, Filip Šír <[log in to unmask]> wrote:
> Dear colleagues,
> we are now in process of research George Voskovec and Jan Werich recordings
> for OWI during WWII.
> We would like to know if there is any kind of information about archive of
> OWI connect with broadcast to Czechoslovakia. We appreciate your help and
> Many thanks
> Best regards
> Filip Sir
> Czech Republic