Here's a neat example of classical interactivity: the Berlin Cello Challenge.
My first score was truly abysmal. My one excuse is that the instructions were a little vague. What you want to do is move the big white circle with your mouse. But your cursor can be anywhere on the screen--you don't have to place it directly on the circle.
Ladies and gentlemen, start your cellos.
Well, I don't think I'll ever play a bow instrument. Of course holding a cello with your knees as you bow is probably easier than holding a computer.