As a freshman at MIT, I participated in MIT's 2.00b, "Toy Lab", class. For our final project, my group developed a set of blocks that each play a different note when your hand is passed over them. (IR proximity detection). The blocks can be stacked to create chords or generally arranged so kids can create their own instrument that's intuitive to them. Please see this page for more detailed information about this project and for a video of our final presentation!