The dun-dun comes from Law and Order, the American police procedural and legal drama created by Dick Wolf that premiered on NBC in 1990. The metallic two-note sting was used as a scene transition throughout the original series and its spinoffs, becoming as recognizable as the show itself. Through reruns, parodies and true-crime coverage it entered everyday pop culture, then spread further as a meme on YouTube and TikTok. Editors still use it because two notes instantly tell viewers something serious just happened.