Want to play the xylophone but don’t want to learn how? [Rachad]’s automatic xylophone might be just the ticket. It uses homemade solenoids to play tunes under computer control. Think of it as ...

vibrate more slowly and make lower-pitched sounds. Shorter objects vibrate faster and make higher-pitched sounds. When Xena strikes the bottles with a metal spoon, she causes the bottles and the water ...