The rainstick is a percussion instrument that can be classified as a shaken idiophone. The rainstick is generally used to create the sound effects of rain or, when shaken, a sound similar to the maracas.
It consists of a long, hollow tube, capped at both ends and filled with small pellets of some sort (possibly pebbles, sand, seeds, dried beans, etc.). Numerous small pins are placed along the length of the inside of the tube and are arranged inwards toward the center of the tube. When the rainstick is turned end over end, the pellets fall to the opposite end of the tube, creating the sound of a rain storm as they bounce off the pins. Although the instrument is not intended to be literally shaken, it is turned from one end to another to allow the pellets to fall from one end to the other creating a shaking movement within the instrument. Turning the rainstick over at different angles provide different sounds and speeds of the pellets moving through the tube.
It is generally thought that the rainstick was invented by Chilean tribes in South America. The instrument was believed to evoke the rain spitits. The early rainsticks were created from dead, dried cactus with the thorns pushed inward. They filled the inside was filled with pebbles, lava rock, seeds, sand, and other materials that were readily available. When turned upside down it created a rain-like sound as the objects inside cascaded over the thorns. It was both rhythmic and very soothing. They also found that placing different objects inside the tube would result in different sounds. The instrument was eventually used for ceremonial music when dancing and were decorated with symbols consistent with rain, weather, crops, and the spirits that rule them. Similar instruments can be found in Africa that use use gourds in place of the cactus.