The Klingon tradition of sung drama, full of battle, honour and doomed love, beloved by Worf and typified by works such as Aktuh and Maylota.
Klingon opera is the great musical form of the Klingon Empire. Its works are loud and emotional and deal with war, honour, betrayal and love, and Klingons expect an audience to feel them as strongly as a battle.
Worf is its most devoted listener in the series. In Unification II he finds that the musician Amarie knows the themes from Aktuh and Maylota and sings along with her. On Deep Space Nine his fondness for opera recordings is a running detail, and Jadzia Dax, who knows Klingon culture through Curzon, shares it.
References recur wherever Klingons appear, including B'Elanna Torres's mixed feelings about her heritage in Voyager and Worf's later years in Picard. The works themselves are rarely heard for more than a few bars.