My non-dance-aficionado friends have a saying: If you're going to take me to a ballet, make it one of the best. They have a point: If you want to dive deeper into classical music, you start with Mozart or Beethoven. Thing is, most of the time, the creators of "the best" are already dead and their works have become lofty, durable standards—not fresh, of-the-moment creations. That's why modern choreographer Mark Morris matters. Very much alive and kicking at 54, Morris has been creating compelling, instant classics since his early twenties.