Many thanks to SWLing Post contributor, Martin Kraft, who shares the following:

Here’s something for the history buffs, an online searchable archive of Radio Free Europe/Radio Liberty broadcasts to the USSR from 1953-1995:

http://www.radioworld.com/article/radio-liberty-munich-period-russian-broadcasts-available/278953

This is brilliant, Martin! I just started searching through the recordings at the Open Society Archives–an impressive collection. Thanks again!