Children are completely blown away by this machine. They keep saying, "wow! I can't believe this!" So I tell them, "maybe some of you will become a scientist or a computer engineer one day, but it doesn't mean that you can't continue to think of cool ways to compose music and amaze the world!" =)
By the way, to answer children's question "How'd they do that?" Here's how the virtual instrument is built on computer.
Anyhow, composing the traditional way is still easier for children to fathom. To make this experience more fun and rewarding, many famous symphony orchestras around the world have put in a lot of resource into developing their kids sites. When it comes to understanding the elements of music and the basics of music composition, The San Francisco Symphony's Kids Site is certainly the best!