There's a song that's been played continuously since 1916 - Apparently.
Since June 1916, "The Entertainer" by Scott Joplin has been played continuously at a St. Louis, Missouri, movie theater. According to the theater's staff, the song has been playing for over 100 years, with the original 78 rpm record being replaced by a digital version in the 1980s. The tradition is said to have begun when a theater owner played the song to entertain patrons while the main movie was being set up.