Mozart wrote 19, I think. They are quite wonderful, fun to play also. And endlessly challenging. You can always play them better, even when they seem perfect, there's something more that can be done. Well, I guess that's always true, but sometimes M's accompaniments are simple enough that it seems like there's not much to do, but then there are all these deeper levels... anyway, what else? Oh, well, Bach and Handel! The violin/keyboard works are just spectacular when played stylishly. They're so good that even with a drippy interpretation, it's great music. My current favorites: Rachel Podger & Trevor Pinnock, and Andrew Manze & Richard Egarr. Marvelous!