At Marienbad in the summer of 1845 he laid down the outlines of his plan, and in the winter ensuing he wrote the book and invented some of the melodic ideas. He began the actual composition of the opera with the narrative of Lohengrin in the final scene, because, like the ballad of Senta, that monologue contained the most significant musical germs in the whole score. While living at Grossgraufen, near Pilnitz, he wrote the music of the third act between September 9, 1846, and March 5, 1847. The first act was composed between May 12 and June 8, 1847, and the second act between June 18th and August 2d of the same year. The prelude was finished on August 28, 1847, and the instrumentation was made during the following winter and spring. The score of the opera was not published for several years, because Meser, who had printed the previous works of the composer, had lost money by the ventures. Breitkopf & Härtel subsequently secured the score at a small price, not because they were niggardly in offering, but because Wagner's works had no large market value at the time, and he was anxious to sell, being in his chronic condition of financial embarrassment.

The Lohengrin poem gives the story thus: Elsa, daughter of the Duke of Brabant, is left in care of Frederic of Telramund. He aspires to her hand, but she refuses him. He then accuses her before the Emperor of having promised to be his wife and having broken the promise. The Emperor declares that the case must be tried by the ordeal of battle. A passing falcon falls at Elsa's feet with a bell tied to its leg. In her agitation she rings the bell. The sound reaches Monsalvat, where it acts as a summons to Lohengrin, the son of Parzival. A swan appears on the river and Lohengrin knows that he is ordered to go with it. On arriving at Antwerp, five days later, Lohengrin is received with honour, and with Elsa sets out for the court of the Emperor at Mayence. There the combat is fought and Telramund defeated. Lohengrin marries Elsa, having extracted from her the promise not to ask his name or country. They live together two years. Then in a joust Lohengrin conquers the Duke of Cleves and breaks his arm. The Duchess of Cleves sneers at Lohengrin because no one knows who he is. This preys on the mind of Elsa till she asks the fatal question. Then Lohengrin, in the presence of the Emperor and the Court, tells his story, steps into the swan-boat and vanishes.

The story of the "Chevalier au Cygne," as found in the Grimm version also, is evidently a combination of two legends. The first deals entirely with the transformation of human beings into swans, and the second with the Swan-Knight. The mother-in-law of a queen, out of hatred, endeavours to make away with her seven children, each of whom was born with a silver chain about its neck, and to throw suspicion on the queen. She gives them to a knight to slay, but he contents himself with leaving them in a wood, where they are found and cared for by a hermit. The king's mother subsequently learns that the children are still alive, and sends a servant to kill them and bring the chains as evidence. He finds six children, one having gone on a short journey with the hermit, and when he takes the chains off their necks they turn into swans and fly away. The king's mother now brings the false accusation against the queen, and the king declares that, unless a champion can be found to establish her innocence, she must die. An angel goes to Helyas, the son who was not found by the servant, and tells him who he is and of his mother's danger. Helyas goes to Court, declares himself, fights for his mother, and conquers. The chains are brought forth, the six swans fly in, Helyas puts the chains around their necks, and they resume their human forms.

Subsequently Helyas sees a swan appear, drawing a boat, and knows that he is summoned. At Nimwegen he finds that before the Emperor Otto the Duchess of Bouillon has been accused by her brother-in-law of poisoning her husband. The Emperor has ordered the settlement of the case by the ordeal of combat. Helyas defends the Duchess, overthrows her accuser, marries her daughter, and becomes the father of Godfrey of Bouillon. After seven years the Duchess asks the fatal question, and Helyas, without answering it, goes away forever in his swan-boat. The reader will easily discover in the latter part of this story how the Lohengrin legend has been used to manufacture a supernatural father for Godfrey of Bouillon. It was not at all uncommon for the poets of the mediæval period thus to celebrate the mighty.

We have now before us the chief materials out of which Wagner made his beautiful dramatic poem, for the story of Wolfram's "Parzival" served principally to set him on the track, and to make suggestions as to the character of Elsa. That story tells simply that the Duchess of Brabant refused to be the wife of any man save him whom God should send her, and so Lohengrin came and the marriage took place, with the stipulation that he should not be asked his name or race. After some years she asked the fatal question and he returned to Monsalvat.

The Elsa of Wolfram was evidently inclined to become a nun, but in two lines of the "Parzival" Wagner found a suggestion as to her nature of which he made eloquent use in his first act:

"In God was her trust, whatever men might in their anger speak,
And, guiltless, she bare the vengeance her folks on her head would wreak."

The absolute confidence of Wagner's Elsa in the readiness of Providence to send her the knight of whom she had dreamed and her unresisting attitude in the presence of her accuser and her king were certainly drawn from these lines of Wolfram's.

From the story of the Swan-Knight he gathered the idea of the transformation of a human being into a swan by a malignant woman, and his tremendously dramatic development of this idea is seen in the plot of his opera. The accusation of Telramund is increased by the assertion that Elsa has murdered her brother, a suggestion drawn, of course, from the accusation against the queen in the "Chevalier au Cygne." He has in reality been transformed into a swan by Ortrud, the wife of Telramund, a character wholly invented by Wagner. It is she who performs the office attributed in the old story to the Duchess of Cleves, that of inspiring distrust and questionings in the mind of Elsa. The character of Telramund is the merest sketch in the sources of the drama and its individuality is entirely the result of Wagner's dramatic skill.