The term 'Lights Out Bugle Tune' is a reference to the bugle call 'Taps', which is a four-note melody played at dusk, during flag ceremonies, and at military funerals. It is also known as the 'Day Is Done' bugle call, and is used to signal the end of the day. The tune is believed to have originated during the American Civil War, and has since become an iconic symbol of remembrance and respect.