In a real-life example of Mickey and Judy deciding to put on a show in somebody's barn, Dan and Barbara Glenn, owners of the real-life Mystery House Publishing Company decide to preview books they were considering publishing as radio plays, with the company's staff pitching in by writing the adaptations, acting all the roles, doing the sound effects.
At least that's how the legend goes. In reality it is not known whether the publishing company or the Glenns actually existed.
The radio show reportedly began in 1929 and ran through 1951, but not continuously. Recording are rare -- about 32 episodes survive, most from the mid-Forties.
(It should be noted that there was a Mystery House publishing company from 1940 to 1948 as an imprint of Arcadia House. Authors included Frank Gruber (as "Stephen Gould"), "Anthony Gilbert," Barry Perowne, Peter Cheney, "E. C. R. Lorac," William G. Bogart, William Gray Beyer, Sydney Horler, Sam Merwin, Jr., Oscar J. Friend (as "Owen Fox Jerome"), John Roebert, Frank Kane, Amelia Reynolds Long, along with a host of lesser writers. They published over seventy books for the library trade during this period. Samuel Curl, the publisher, went bankrupt in 1948 and sold Arcadia House to Phoenix press. Curl managed to reorganize in 1950 and later entered into a partnership with Thomas Bouregy to form Bouregy & Curl. Curl issued thirteen books under the Mystery House imprint from 1952 to 1956 when Curl ran out of money, dissolved his partnership with Bouregy, and exited publishing. All Mystery House Books from 1957 to 1959 were published by Bouregy. At no time during this entire period was there any mention of the Glenns and no book issued under any of the titles used in the Mystery House radio program.)
Anyway, here's the earliest episode of Mystery House that I could find online.