Music for the promos of the show

I have a music question. Back when AMC was a good channel and was showing "Remember WENN" when they had previews for the up-coming episodes, or promos for the show between movies. What was the music they played? It's not the theme to the show, but something else that I take to be a song from the 40's, because every so often I will hear that song as back ground music being used in stuff set during the 40's. Does anyone know what I'm talking about and if so what the song was? Thanks