The 1691 first performed semi-opera King Arthur, or The British Worthy (King Arthur or The British hero) is based on a 1684 written libretto by John Dryden (1631-1700). This acclaimed poet and playwright in his lifetime was found in 1690 by the music of the also famous composer Henry Purcell (1659? -1695) So impressed that he offered his revised King Arthur Purcell to set to music. The result was the first semi-opera, which was not based on an existing spectacle and still connected spoken drama with musical scenes. King Arthur remained in the repertoire until well into the 18th century, with the popularity especially the intimate and innovatively designed music Purcell was due. Content, Dryden moved away from the continuously embellished since the Middle Ages King Arthur saga with the Knights of the Round Table and the Holy Grail, rather, unfolds a story about love and war. The blind Emmeline is the daughter of the Duke of Cornwall and Conon of King Arthur as coveted as the Saxon King Oswald. Territorial reasons lead to the first military confrontation of the two - Oswald subject, but it can kidnap Emmeline. Now it becomes the cause of the war: the battles, the counterparties of magicians and spirits are supported, especially Merlin on Arthur's side, the quasi represents the only remnant of the famous Arthurian legend. Oswald subject again, and Arthur can Emmeline win for themselves. Arthur shows kindness and pardoned Oswald, leaving Merlin to think of a united Britain under a just ruler.