Here's an interesting site that came along in an old time radio mailing list I'm a member of.
OTR enthusiast Vince Long obtained about 100 reel to reel tapes, many early Scotch paper-based tapes, that were recorded of network and local radio shows in the Billings, Montana area in the early 1950s. They're a fascinating look at local radio and what an average listener might have been tuned to at the time. The collection includes many shows not previously in circulation and include music, variety, news and sports shows. All are available in downloadable MP3 format.