There's a song that's been played continuously since 1914 - Apparently.
The song "Ave Maria" by Franz Biebl has been broadcast continuously on a German radio station since the outbreak of World War I. It was first aired on August 4, 1914, and has been playing ever since, with a 30-second pause every hour to allow for news updates. The song is now known as "The Eternally Playing Song" and has become a symbol of German radio broadcasting tradition.