"Who knows what evil lurks in the hearts of men? The Shadow knows!" The opening lines of the "Detective Story" program captivated listeners and are instantly recognizable even today. Originally the narrator of the series of macabre tales, the eerie voice known as The Shadow became so popular to listeners that "Detective Story" was soon renamed "The Shadow," and the narrator became the star of the old-time mystery radio series, which ran until 1954.
I could only find 4 that were listed as Public Domain.