All sound comes from vibrations. A vibration is a quick shake. It starts when something is bumped.

A string instrument is made of wood. Its strings vibrate to make the sound. Its hollow body makes the sound louder.

A violin has a bow. The bow is a stick with a ribbon of hair.

You pluck a harp with your fingers. Its strings shake.

Drums make sound when they are hit. Some things make sound when they are shaken or scraped.

Brass players buzz their lips. They buzz them into a metal mouthpiece. That is how the sound starts.

Most woodwinds have a reed. It is a small piece of cane or wood. It shakes when air goes across it.

A flute has no reed. Its sound comes from air that hits an edge. The air in the tube shakes.

Felt hammers hit the metal strings of a piano. That makes the sound.

Some flutes were made from bone and ivory. They were found in caves in Germany. They are about 40,000 years old. They are among the oldest known instruments.

An orchestra has four groups of instruments. They are strings, woodwinds, brass and percussion.

Words to know

• vibrate: shake fast
• reed: thin cane
• percussion: hit instruments
• flute: wind instrument
• flutes: wind instruments
• woodwinds: a group