For many years now, I have used background music in my roleplaying game sessions. Music is a prefect tool to help to set a certain mood. For my last Trail of Cthulhu game, which was set into the late 1930s, I used a mix of movie soundtracks (especially the “A Nightmare on Elm Street” soundtrack works great for any horror game) and 1930s jazz music. I didn’t own any 1930s music, so I had to lend a few CDs from a friend who’s a big fan of jazz music.
But now I found a free source of music from the early 20th century (thanks to the Propnomicon blog). Archive.org has thousands of recordings from 78 rpm records and even phonograph cylinders.
The above song is 1920s big band music performed by Abe Lyman and his band.