As a footnote to my little piece of Mozart history, in my last post, here’s a Canaletto painting, done in 1754, called “London: Interior of the Rotunda at Ranelagh.” It shows a concert. Notice how informal it is, and in some ways how much like a modern rock club. A few people are gathered by the stage, listening (I’d think) intently. Others are scattered through the space, talking and hanging out. It’s easy to see how in an atmosphere like this, people would feel free to clap right in the middle of the music, if they heard something that they liked. Our concept of “classical music” simply didn’t exist yet, and people listened quite informally.