It took him four tries to get it right, and it wasn't until Anna Milder, the soprano who played Leonora, took him aside and relentlessly critiqued it that he made the changes that made it a success. Beethoven didn't like taking advice from anybody, but Anna had been in the business since her teens, and she knew her stuff.
Haydn said she had a voice like a house. In her later years when she formed a professional relationship with Schubert, she looked like a house. She must have weighed 300 pounds.