Richard Wagner had already established himself well in Germany, even after having to flee Saxony due to his left-wing politics and participation in the May 1849 uprising in Dresden. Having settled first in Zurich, then in Paris, he continued composing, including an adaptation of his 1845 opera Tannhäuser for the Paris Opera. Apart from translating the libretto into French, he altered the structure of the opera to better suit the French stage.
It was customary at the Paris Opera for there to be a ballet, usually in the penultimate act, but Wagner tacked it onto the Overture instead. Wagner did not wish to disrupt his plot with an unnecessary dance number, and it made dramatic sense to add a bacchanale to the opening scene at the Venusberg. (As a side note, this also caused him some trouble, as the direct translation of that term into French also happened to be a euphemism for the mons pubis.) There were numerous other alterations and additions to the 1845 Dresden version, and Wagner was closely inv