Some scholars have theorized that Rossini retired from composing operas after Guillaume Tell because he disliked the direction opera was going and the kinds of things he had to write in order to maintain his popularity. He became really upset with Wagner’s music. Two of his comments are very well known:
Wagner has lovely moments but awful quarters of an hour.
One cannot judge ‘Lohengrin’ from a first hearing, and I certainly do not intend to hear it a second time.
Those were his polite comments. Once he was talking with a singer about Wagner’s music when he decided to demonstrate what it sounded like. Opening the piano, he sat heavily on the keyboard and said, “There! That’s the music of the future.”